A display brightness correction method and system
By acquiring the luminance and chromaticity values of the display under different PWM conditions, calculating the theoretical gamma curve and forming a mapping table, the problem of inaccurate calibration of LED displays was solved, achieving precise calibration and improved performance of the display.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING KYSTAR TECH CO LTD
- Filing Date
- 2025-01-22
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies cannot accurately calibrate LED displays, resulting in uneven grayscale variations, gray skipping, banding, and gamma value deviations, leading to poor display quality.
By acquiring the red, green, blue, and white luminance and chromaticity values of the display under different PWM conditions, the theoretical target display gamma curve is calculated. The actual measured values that are closest to the theoretical gamma target red, green, and blue luminance values are found to form a gamma correction mapping table, and the lookup table is output to correct the display.
It enables precise calibration of LED displays, reduces luminance and colorimeter measurement errors, and improves the consistency and accuracy of display effects.
Smart Images
Figure CN119993035B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of display testing technology, and in particular to a method and system for calibrating the brightness and color of a display. Background Technology
[0002] In recent years, display technology has advanced rapidly, with the development of high-density, small-pitch LED displays being particularly noteworthy, and the resulting improvement in display effects has attracted much attention. However, in the LED display field, due to the different LED driver chips used in various displays, the grayscale transition effects vary significantly. Common issues include uneven grayscale changes such as gray skipping and banding, and some displays also exhibit large deviations from standard gamma values and color shifts in grayscale transitions, failing to meet the optimal viewing experience for the human eye.
[0003] Furthermore, because LED displays are composed of self-emissive dot matrices, they offer higher brightness and contrast compared to traditional CRT and LCD displays. In existing technologies, even using standard luminance and colorimeter measurements, a certain amount of error still exists. Correction is achieved by measuring the display's color with an industry-standard luminance and colorimeter and establishing a relationship between the input image and the actual measurement. However, even with standard luminance and colorimeter measurements, a certain amount of error remains, which may affect the accurate evaluation of LED display performance, thus making precise calibration impossible. Summary of the Invention
[0004] Based on this, and in response to the aforementioned technical problems, a method and system for luminance and color calibration of a display are provided to solve the problem that existing technologies cannot accurately calibrate LED displays.
[0005] In a first aspect, a method for calibrating the luminance and chromaticity of a display, the method comprising:
[0006] When the monitor displays a preset image, the actual luminance and chromaticity values of red, green, blue, and white measured by the luminance and chromaticity meter under different PWM conditions are obtained.
[0007] The theoretical target display gamma curve is calculated based on the actual measured luminance values of white under different PWM conditions.
[0008] For each level of the theoretical gamma target in the theoretical gamma curve, the measured red, green, and blue color coordinates of the PWM value corresponding to the same measured white luminance value are obtained; the red, green, and blue luminance values of each level of the theoretical gamma target are calculated based on the measured red, green, and blue color coordinates corresponding to the same measured white luminance value of each level of the theoretical gamma target, and the white luminance value of each level of the theoretical gamma target.
[0009] Find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level, and obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level. Establish a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level and the theoretical gamma target luminance values at each level, and output the gamma correction lookup table.
[0010] Optionally, after obtaining the actual measured luminance and chromaticity values of red, green, blue, and white under different PWMs by the luminance and chromaticity meter, the method further includes: preprocessing the actual measured luminance and chromaticity values of red, green, blue, and white under different PWMs, wherein the preprocessing includes: background removal, filtering, and filtering outliers.
[0011] In the above scheme, optionally, after preprocessing the measured luminance and chromaticity values of red, green, blue, and white under different PWMs, the scheme further includes: performing linear interpolation on the measured luminance and chromaticity values of red, green, blue, and white under different PWMs to obtain luminance and chromaticity values of red, green, blue, and white with continuous different PWM distributions.
[0012] In the above scheme, optionally, after obtaining the actual measured luminance values of red, green, blue, and white under different PWMs by the luminance colorimeter, the method further includes: calculating the theoretical white luminance value based on the actual measured luminance values of red, green, and blue under the same PWM, and using the theoretical white luminance value to correct the actual measured white luminance value.
[0013] Optionally, in the above scheme, the calculation of the theoretical target display gamma curve based on the obtained actual measured maximum PWM luminance value of white includes:
[0014] The target value for maximum brightness will be the white luminance value obtained from the actual measured maximum PWM.
[0015] Select any curve as the target display gamma curve, including: HDR, HLG or PQ perception curve;
[0016] The target display gamma curve uses a piecewise function, employing a linear function near 0, the slope of which is determined by the display's minimum quantization precision; the mid-to-high range is the theoretical curve, ensuring continuity and smoothness at the segmentation points.
[0017] In the above scheme, optionally, the piecewise function satisfies the following requirements:
[0018]
[0019] f a (x0)=f b(x0)
[0020] y = f a (x), x≤x0
[0021] y = f b (x),x>x0
[0022] To ensure that the piecewise functions are equal at x0, the gamma curves at mid-to-high points are adjusted:
[0023]
[0024] Among them, f a f is a linear function b This is the theoretical curve.
[0025] Optionally, in the above scheme, the calculation of the theoretical gamma target red, green, and blue brightness values for each level is performed using the following formula:
[0026]
[0027] The conversion formulas between XYZ and cx, cy, and Y are as follows:
[0028]
[0029] Y = Y
[0030]
[0031] Among them, X w Y w Z w It is the theoretical white chromaticity value; R cx R cy G cx G cy B cx B cy , which are RGB color coordinates.
[0032] Secondly, a display luminance and chromaticity correction system, the system comprising:
[0033] Data acquisition module: used to acquire the actual luminance and chromaticity values of red, green, blue and white under different PWM when the monitor displays the preset screen;
[0034] Theoretical target display gamma curve calculation module: used to calculate the theoretical target display gamma curve based on the acquired actual measured luminance values of white under different PWM conditions;
[0035] The theoretical gamma target red, green, and blue luminance value calculation module: This module is used to obtain the measured red, green, and blue color coordinates under the PWM value corresponding to the measured white luminance value of each theoretical gamma target in the theoretical target display gamma curve; and to calculate the red, green, and blue luminance value of each theoretical gamma target based on the measured red, green, and blue color coordinates corresponding to the measured white luminance value of each theoretical gamma target, and the white luminance value of each theoretical gamma target.
[0036] Gamma correction table output module: used to find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level, and to obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level. It then establishes a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level and outputs a gamma correction lookup table.
[0037] Thirdly, a computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the display luminance and chromaticity correction method described in the first aspect.
[0038] Fourthly, a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the display luminance and chromaticity correction method described in the first aspect.
[0039] This application has at least the following beneficial effects:
[0040] This application calculates the theoretical target display gamma curve by actually measuring the luminance and chromaticity values of red, green, blue, and white under different PWM (Power Width Modulation) conditions. Based on the measured white luminance and chromaticity values under different PWM conditions, it obtains the measured red, green, and blue color coordinates under the corresponding PWM value for each theoretical gamma target level. Then, using the measured red, green, and blue color coordinates corresponding to the measured white luminance values for each theoretical gamma target level, and the theoretical white luminance and chromaticity values, it calculates the red, green, and blue luminance values for each theoretical gamma target level. This overcomes the inherent error associated with using a standard luminance and chromaticity meter. A mapping relationship is established between the measured red, green, and blue luminance values closest to the theoretical gamma target luminance and chromaticity values at each level and the theoretical gamma target luminance and chromaticity values at each level, outputting a gamma correction lookup table. This gamma correction mapping table allows for accurate output of the desired image. This method enables precise display calibration. Attached Figure Description
[0041] Figure 1 A schematic flowchart illustrating a display luminance and chromaticity correction method according to an embodiment of this application;
[0042] Figure 2 A detailed flowchart illustrating a display luminance and chromaticity correction method is provided in one embodiment of this application.
[0043] Figure 3 This is a schematic diagram illustrating the display of a gamma curve using an HLG curve as a theoretical target, provided as an embodiment of this application. Detailed Implementation
[0044] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0045] In one embodiment, such as Figure 1 As shown, a method for calibrating the luminance and chromaticity of a display is provided, including the following steps:
[0046] Step S1: Obtain the actual luminance and chromaticity values of red, green, blue, and white under different PWM conditions when the monitor displays the preset image.
[0047] In step S1, a standard luminance and chromaticity meter is connected to the main control device, such as a computer, to measure the progressive PWM luminance and chromaticity values of the red, green, blue, and white (RGBW) colors on the display panel. The measurement time can also be reduced by adjusting the sampling PWM interval, but the interval value needs to be recovered by interpolation in subsequent processing when sampling at intervals.
[0048] After step S1, upon receiving the measured RGBW luminance and chrominance values, a background removal operation is first performed. This involves subtracting the measured value when the PWM signal is 0 or the screen is black from each measured value. Then, filtering is applied to remove measurement errors, noise spikes, and other anomalies, aiming to reduce deviations introduced by measurement accuracy or stability. Generally, as the PWM increases, the measured luminance increases accordingly. Therefore, outliers can be eliminated by checking if the current value is greater than the previous PWM luminance value within the adjacent range but less than the next PWM luminance value, iterating through the measurement data sequentially. For chrominance coordinates, considering that monochromatic chrominance coordinates do not exhibit abrupt changes, smoothing methods such as median filtering and mean filtering are used.
[0049] Then, the PWM-luminance data sampled at previous intervals and the values discarded due to anomalies are interpolated to obtain RGBW luminance and chrominance data with continuous PWM distribution.
[0050] Meanwhile, since the actual measured luminance of white does not equal the theoretically calculated luminance of white, a theoretical white value is calculated to correct the measured value. Given the RGB measured luminance data, the formula for calculating the theoretical white luminance is as follows:
[0051] X r +X g +X b =X w
[0052] Y r +Y g +Y b =Y w
[0053] Z r +Z g +Z b =Z w
[0054] Where XYZ are the tristimulus values of the RGB three primary colors, and the subscript indicates the color.
[0055] Step S2: Calculate the theoretical target display gamma curve based on the obtained actual measured luminance values of white under different PWM conditions.
[0056] First, the white luminance and chromaticity value measured at maximum PWM is used as the target value for maximum brightness to maintain consistent white luminance and chromaticity after gamma correction. Then, a target curve is selected as the gamma curve. For example, a standard curve with a gamma of 2.8 is selected for LED screens, or an HLG or PQ sensing curve is used as the target gamma curve for LED screens whose maximum brightness meets HDR standards. Figure 3 The figure shows the piecewise gamma curve calculated using the HLG curve as the target gamma curve and the measured minimum quantization precision of the hardware.
[0057] Specifically, the target gamma curve can use a piecewise function, for example, a linear function near 0, with the slope determined by the minimum quantization precision of the display; and a theoretical curve in the mid-to-high range, where the segments are continuous and smooth. The piecewise function then satisfies the following requirements:
[0058]
[0059] f a (x0)=f b (x0)
[0060] y = f a (x), x≤x0
[0061] y = f b (x),x>x0
[0062] Meanwhile, to ensure that the piecewise functions are equal at x0, the medium-high gray gamma curve is adjusted as follows:
[0063]
[0064] Among them, f a f is a linear function b This is the theoretical curve.
[0065] Step S3: For the white luminance and chromaticity value of each theoretical gamma target in the theoretical target display gamma curve, obtain the measured red, green, and blue color coordinates under the PWM value corresponding to the same measured white luminance value; calculate the red, green, and blue luminance value of each theoretical gamma target based on the measured red, green, and blue color coordinates corresponding to the same measured white luminance and chromaticity value of each theoretical gamma target, and the white luminance and chromaticity value of each theoretical gamma target;
[0066] In step S3, the index of the white luminance value of the theoretical gamma target at each level in the interpolated PWM white luminance value is found, and the RGB color coordinates under that index are obtained. The luminance of the RGB primary colors is calculated by using the output RGB color coordinates and the luminance and color coordinates of the target white at each theoretical gamma level.
[0067]
[0068] The conversion formulas between XYZ and cx, cy, and Y are as follows:
[0069]
[0070] Y = Y
[0071]
[0072] Among them, X w Y w Z w It is the theoretical white chromaticity value; R cx R cy G cx G cy B cx B cy , which are RGB color coordinates.
[0073] Step S4: Find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level, and obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level. Establish a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level and the theoretical gamma target red, green, and blue luminance values at each level, and output the lookup table for gamma correction.
[0074] In this step, the objective is to find the PWM value in the previous module that is closest to the value in the PWM-luminance interpolated data, output a lookup table for RGB, and use it as a mapping table for gamma correction, which is then sent to the hardware. Based on this gamma correction mapping table, the PWM value is adjusted according to the actual required luminance and color intensity.
[0075] In the aforementioned method for luminance and chromaticity correction of a display, the luminance and chromaticity values of red, green, blue, and white under different PWM (Power Mode) are measured. Based on the measured luminance and chromaticity values of white under different PWM conditions, a theoretical target display gamma curve is calculated. Then, using the white luminance and chromaticity value of the theoretical gamma target at each level of the theoretical gamma curve, the measured red, green, and blue color coordinates under the corresponding PWM value are obtained. Finally, using the measured red, green, and blue color coordinates corresponding to the measured white luminance and chromaticity values of each theoretical gamma target, and the theoretical white luminance and chromaticity value, the red, green, and blue luminance values of each theoretical gamma target are calculated. This overcomes the influence of a certain amount of error inherent in measurements using a standard luminance and chromaticity meter. A mapping relationship is established between the measured red, green, and blue luminance and chromaticity values closest to the theoretical gamma target values at each level and the theoretical gamma target red, green, and blue luminance and chromaticity values at each level, outputting a gamma correction lookup table. This gamma correction mapping table allows for accurate output of the desired image. This method enables precise calibration of the display.
[0076] In one embodiment, a display luminance and chromaticity correction system is provided, the system comprising:
[0077] Data acquisition module: used to acquire the actual luminance and chromaticity values of red, green, blue and white under different PWM when the monitor displays the preset screen;
[0078] Theoretical target display gamma curve calculation module: used to calculate the theoretical target display gamma curve based on the acquired actual measured luminance values of white under different PWM conditions;
[0079] The theoretical gamma target red, green, and blue luminance value calculation module: This module is used to obtain the measured red, green, and blue color coordinates under the PWM value corresponding to the measured white luminance value of each theoretical gamma target in the theoretical target display gamma curve; and to calculate the red, green, and blue luminance value of each theoretical gamma target based on the measured red, green, and blue color coordinates corresponding to the measured white luminance value of each theoretical gamma target, and the white luminance value of each theoretical gamma target.
[0080] Gamma correction table output module: used to find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level, and to obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level. It then establishes a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level and outputs a gamma correction lookup table.
[0081] For specific limitations regarding a display luminance and chromaticity correction system, please refer to the limitations of a display luminance and chromaticity correction method described above, which will not be repeated here. Each module in the aforementioned display luminance and chromaticity correction system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of the computer device, so that the processor can call and execute the corresponding operations of each module.
[0082] In one embodiment, a computer device is provided, which may be a server. The computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements the aforementioned display brightness and color correction method.
[0083] In one embodiment, a computer-readable storage medium is also provided, on which a computer program is stored relating to all or part of the processes in the methods of the above embodiments.
[0084] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.
[0085] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0086] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A method for calibrating the luminance and chromaticity of a display, characterized in that, The method includes: When the monitor displays a preset image, the actual luminance and chromaticity values of red, green, blue, and white measured by the luminance and chromaticity meter under different PWM conditions are obtained. The theoretical target display gamma curve is calculated based on the actual measured luminance values of white under different PWM conditions. For each level of the theoretical gamma target in the theoretical gamma curve, the measured red, green, and blue color coordinates of the PWM value corresponding to the same measured white luminance value are obtained; the red, green, and blue luminance values of each level of the theoretical gamma target are calculated based on the measured red, green, and blue color coordinates corresponding to the same measured white luminance value of each level of the theoretical gamma target, and the white luminance value of each level of the theoretical gamma target. Find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level, and obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level. Establish a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target luminance values at each level and the theoretical gamma target luminance values at each level, and output the gamma correction lookup table.
2. The display luminance and chromaticity correction method according to claim 1, characterized in that, After obtaining the actual measured luminance and chromaticity values of red, green, blue, and white under different PWM conditions by the luminance and chromaticity meter, the method further includes: preprocessing the actual measured luminance and chromaticity values of red, green, blue, and white under different PWM conditions, the preprocessing including: background removal, filtering, and filtering outliers.
3. The display luminance and chromaticity correction method according to claim 2, characterized in that, After preprocessing the measured luminance and chromaticity values of red, green, blue, and white under different PWMs, the method further includes: performing linear interpolation on the measured luminance and chromaticity values of red, green, blue, and white under different PWMs to obtain luminance and chromaticity values of red, green, blue, and white with continuous different PWM distributions.
4. The display luminance and chromaticity correction method according to claim 3, characterized in that, After obtaining the actual measured luminance values of red, green, blue, and white under different PWMs by the luminance colorimeter, the method further includes: calculating the theoretical white luminance value based on the actual measured luminance values of red, green, and blue under the same PWM, and using the theoretical white luminance value to correct the actual measured white luminance value.
5. The display luminance and chromaticity correction method according to claim 1, characterized in that, The calculation of the theoretical target display gamma curve based on the acquired actual measured maximum PWM luminance value of white includes: The target value for maximum brightness will be the white chromaticity value obtained from the actual measured maximum PWM. Select any curve as the target display gamma curve, including: HDR, HLG or PQ perception curve; The target display gamma curve uses a piecewise function, employing a linear function near 0, the slope of which is determined by the display's minimum quantization precision; the mid-to-high range is the theoretical curve, ensuring continuity and smoothness at the segmentation points.
6. The display luminance and chromaticity correction method according to claim 5, characterized in that, The piecewise function must meet the following requirements: f a (x0)=f b (x0) y=f a (x),x≤x0 y=f b (x),x>x0 To ensure that the piecewise functions are equal at x0, the gamma curves at mid-to-high points are adjusted: Among them, f a f is a linear function b This is the theoretical curve.
7. The display luminance and chromaticity correction method according to claim 1, characterized in that, The theoretical gamma target red, green, and blue brightness values for each level are calculated using the following formula: The conversion formulas between XYZ and cx, cy, and Y are as follows: Y = Y Among them, X w Y w Z w It is the theoretical white chromaticity value; R cx R cy G cx G cy B cx B cy , which are RGB color coordinates.
8. A display luminance and chromaticity correction system, characterized in that, The system includes: Data acquisition module: used to acquire the actual luminance and chromaticity values of red, green, blue and white under different PWM when the monitor displays the preset screen; Theoretical target display gamma curve calculation module: used to calculate the theoretical target display gamma curve based on the acquired actual measured luminance values of white under different PWM conditions; The theoretical gamma target red, green, and blue luminance value calculation module: This module is used to obtain the measured red, green, and blue color coordinates under the PWM value corresponding to the measured white luminance value of each theoretical gamma target in the theoretical target display gamma curve; and to calculate the red, green, and blue luminance value of each theoretical gamma target based on the measured red, green, and blue color coordinates corresponding to the measured white luminance value of each theoretical gamma target, and the white luminance value of each theoretical gamma target. Gamma correction table output module: used to find the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level, and to obtain the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level. It then establishes a mapping relationship between the PMM value corresponding to the actual measured red, green, and blue luminance values that are closest to the theoretical gamma target red, green, and blue luminance values at each level and outputs a gamma correction lookup table.
9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.
10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 7.