A method and system for brightness correction of an LED display screen

Abstract

The application discloses an LED display screen brightness correction method and system, and belongs to the technical field of LED display.The application solves the technical problem that the existing LED display screen correction technology is difficult to collect correct brightness data, so that the correction result is inaccurate.The method changes the previous brightness correction mode, and performs brightness correction on LED units constituting an LED screen.In a state that the LED screen is not assembled into a large block, brightness data in a thermal equilibrium state is calculated through a temperature prediction model (formula) according to instantaneous collection data of an environmental temperature collected by an automatic production line, and brightness correction is performed according to the data, so that a display effect without deviation can be obtained, and lighting to an expected brightness is not needed, then, the collection and correction step is performed on the basis, the prediction model is calculated for the same type of product, and is suitable for any module of the type of product, and the LED units after the brightness correction can be spliced at will in the state that the screen is assembled into a whole.

Description

Technical Field

[0001] This invention belongs to the field of LED display technology, and specifically relates to an LED display screen brightness correction method and system. Background Technology

[0002] LED displays boast technological advantages such as high brightness, wide color gamut, and the ability to be infinitely spliced. However, during continuous illumination, because the energy conversion efficiency of LEDs is typically only 20% to 50%, more than half of the electrical energy is directly converted into heat through non-radiative recombination, causing the PN junction temperature to rise rapidly. As the junction temperature increases, the dominant wavelength of its emitted light shifts towards longer wavelengths, resulting in white balance imbalance and color coordinate shift in the LED display.

[0003] Existing LED display calibration technologies typically collect brightness data continuously after the screen is turned on. The collected data is randomly positioned on the brightness decay curve, resulting in inconsistent color shifts after the screen reaches thermal equilibrium. To prevent color shifts in LED displays at thermal equilibrium, the common method is to illuminate the screen to the desired brightness and then perform calibration based on this. However, because LED display brightness is highly sensitive to temperature changes, area-based data acquisition is inaccurate for large-size LED displays, while intermittent data acquisition is time-consuming and causes screen temperature drops, making it difficult to collect accurate brightness data and resulting in inaccurate calibration results. Summary of the Invention

[0004] To address the technical problem that existing LED display calibration technologies struggle to acquire accurate brightness data, resulting in inaccurate calibration results, this invention provides an LED display brightness calibration method and system.

[0005] Firstly, the method specifically includes:

[0006] Before splicing, each LED module of a certain model that makes up the LED display screen is subjected to brightness calibration.

[0007] The brightness correction method involves establishing a mapping relationship between the brightness matrices acquired by the red, green, and blue chips of a single LED module under X, Y, and Z filters and the corresponding acquired temperature matrices. Since the brightness of the red chip in the single LED module is approximately zero under the Z filter, no mapping relationship is established. This results in eight identical mapping formulas, from which any temperature matrix can be used for correction. To obtain the corresponding brightness matrix After establishing the mapping formula, the temperature matrix corresponding to when a single LED module reaches thermal equilibrium is used. Without requiring measurement, the predicted brightness matrix of a single LED module when it reaches thermal equilibrium is obtained. Obtain the predicted brightness matrix when a single LED module reaches thermal equilibrium. Then, based on the predicted brightness matrix when a single LED module reaches thermal equilibrium... Brightness calibration of individual LED modules;

[0008] After brightness calibration of each type of LED module, the LED modules are spliced ​​together to form an LED display screen.

[0009] Furthermore, the mapping formula is as follows: ,in Represents the initial brightness matrix. … For the fitting matrix, This is the initial temperature matrix.

[0010] Furthermore, when performing brightness calibration of the LED display screen, it is ensured that each type of LED module constituting the LED display screen is at the same initial acquisition temperature.

[0011] Furthermore, in middle, The value is 3.

[0012] Further, collection Brightness matrix of red, green and blue chips in a single LED module under X, Y and Z filters With the corresponding temperature matrix The theoretical brightness matrix is residual This indicates the deviation between the measured value and the theoretical value;

[0013] Minimize, that is, for Find them separately , , , Taking the partial derivatives of and setting them equal to 0, we obtain the system of linear equations:

[0014] Solving this system of equations will yield the optimal fitting coefficient matrix. , , and .

[0015] Furthermore, the eight mapping formulas with the same representation are combined and expressed as follows:

[0016]

[0017] subscript , , , , , , and These correspond to the fitting relationships of the luminance and temperature matrices of the red component under the X filter, the green component under the X filter, the blue component under the X filter, the red component under the Y filter, the green component under the Y filter, the blue component under the Y filter, the green component under the Z filter, and the blue component under the Z filter, respectively.

[0018] Furthermore, based on the temperature matrix corresponding to when a single LED module reaches thermal equilibrium... Obtain the predicted brightness matrix when a single LED module reaches thermal equilibrium. At this time, N×N modules are built, and the temperature matrix is ​​obtained by taking pictures of the screen with a thermal imager. The acquired images are preprocessed, including image tilt correction, edge extraction and data interpolation. Then, the middle N / 2×N / 2 modules are taken as standard blocks, and the average temperature of the middle N / 2×N / 2 modules is used as the temperature matrix when a single module reaches thermal equilibrium. .

[0019] Furthermore, the brightness matrix is ​​represented by grayscale data captured by a CCD camera, and the temperature matrix is ​​represented by data captured by a thermal imager.

[0020] Secondly, the system includes:

[0021] The data acquisition unit: Before splicing the LED display screen, the brightness matrix and corresponding temperature matrix of the red, green and blue chips of each type of LED single module constituting the LED display screen are collected under the X, Y and Z filters; for multiple LED single modules of the same type, one is selected as a representative.

[0022] The unit used for data calculation calculates the mapping relationship between the brightness matrix and the corresponding temperature matrix of each LED module based on the collected brightness matrix and temperature matrix. However, the brightness of the red chip in the LED module under the Z filter is approximately zero, so no mapping relationship is established. This results in eight identical mapping formulas for each LED module. Therefore, for each LED module, the unit calculates the mapping relationship based on the temperature matrix corresponding to the LED module when it reaches thermal equilibrium. Without requiring measurement, the predicted brightness matrix of a single LED module when it reaches thermal equilibrium is obtained. ;

[0023] Unit for brightness correction: For different models of LED modules, based on the predicted brightness matrix when the LED module reaches thermal equilibrium. Brightness correction is performed on a single LED module to obtain a brightness-corrected single LED module;

[0024] Units used for LED single-module splicing: splicing different models of LED single modules into an LED display screen.

[0025] The beneficial effects of the proposed LED display brightness correction method are as follows: LED screens are often composed of LED units of different models. Traditional LED brightness correction methods involve assembling the LED screen, lighting it to the desired brightness, and then performing data collection and correction. This method leads to inaccurate data collection during the correction of large-size LED displays, as area-based data acquisition is insufficient, and intermittent data acquisition takes a long time, causing the screen temperature to drop, making it difficult to collect accurate brightness data and resulting in inaccurate correction results. This new method changes the previous brightness correction approach by performing brightness correction on the LED units that make up the LED screen. Before assembling into a large LED screen, the instantaneous ambient temperature data collected from the automated production line is used to calculate the predicted brightness data under thermal equilibrium conditions using a temperature prediction model (formula). Brightness correction based on this data yields a color-accurate display effect, eliminating the need for lighting to the desired brightness and then performing data collection and correction. By calculating the prediction model for the same product model, it is applicable to any module of that product model. When assembling into a complete screen, the brightness-corrected LED units can be arbitrarily spliced ​​together. Attached Figure Description

[0026] Figure 1 This is a temperature distribution diagram of a 4×4 box in an embodiment of the present invention;

[0027] Figure 2 These are schematic diagrams of tilt correction before (left) and after (right) in an embodiment of the present invention;

[0028] Figure 3 This is a flowchart of the LED display screen brightness correction method in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the LED display screen brightness correction system in an embodiment of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0031] Example 1

[0032] To address the technical problem of inaccurate calibration results due to the difficulty in acquiring accurate brightness data in existing LED display calibration technologies, this embodiment provides an LED brightness attenuation compensation method. A mapping relationship is established between the brightness matrices acquired by the R, G, and B chips under X, Y, and Z filters and their corresponding temperature matrices. Under the constant temperature conditions of an automated production line, the initial acquisition state of each module or group is identical. Based on the mapping relationship, the brightness (chromaticity) data of the LED under thermal equilibrium can be predicted, and screen calibration for thermal equilibrium is completed in the initial state. Figure 3 As shown, the steps include the following.

[0033] Step 1. Select the LED module to be tested and record the brightness matrix L and temperature matrix T in real time. The mapping relationship between brightness decay and temperature rise is L=f(T), where the brightness matrix is ​​represented by the grayscale value captured by the CCD camera and the temperature matrix is ​​represented by the data captured by the thermal imager.

[0034] Step 2. Although LED brightness and light output power P are linearly related, making the brightness-temperature decay mapping relationship approximately linear, this embodiment uses a polynomial fitting method to construct the brightness decay-temperature rise mapping relationship, considering the influence of various complex environmental variables. ,in … For the fitting matrix, For the initial brightness matrix, Given the initial temperature matrix (ambient temperature), experimental results show that when At that time, this relation is sufficient to accurately represent the mapping relationship.

[0035] Step 3. For the formula in Step 2, multiple sets of data can be measured, but the coefficients obtained each time are not exactly the same. Therefore, the least squares method is needed to fit the coefficients of the cubic polynomial. Let there be a total of Group of measured data, For the ambient temperature matrix, The original brightness matrix at ambient temperature. For the first The measured temperature matrix of the group This corresponds to the measured luminance matrix. Based on known relationships, the theoretical luminance matrix is... residual This indicates the deviation between the measured value and the theoretical value.

[0036] Minimize, that is, for Find them separately , , , Taking the partial derivatives of and setting them to zero, we obtain the system of linear equations: ( represent The sum of squares of the deviations between the measured and theoretical values ​​is the sum of the squares of the deviations from the theoretical values. Minimizing the sum of squares of the deviations from n sets represents the result where the theoretical value is closest to the measured value.

[0037] Solving this system of equations will yield the optimal fitting coefficient matrix. , , and .

[0038] Step 4. Capture images using a CCD camera, and calculate the brightness matrix through positioning, segmentation, and integration. and Since the attenuation coefficients of red, green, and blue LED chips and the brightness data obtained from shooting red, green, and blue (R / G / B) colors using different filters (X / Y / Z) during color correction are different, the attenuation coefficients are calculated separately for LED chips of different colors and components. Therefore, the following results are obtained:

[0039]

[0040] After calculation, the matrix of all fitting coefficients was obtained, where the subscripts... , , , , , , and These correspond to the fitting relationships of the luminance and temperature matrices of the red component under the X filter, the green component under the X filter, the blue component under the X filter, the red component under the Y filter, the green component under the Y filter, the blue component under the Y filter, the green component under the Z filter, and the blue component under the Z filter.

[0041] Step 5. To ensure the accuracy of the collected thermal balance data and eliminate the influence of edge heat dissipation, when performing brightness correction on single modules in the same batch, N×N modules are built, and the temperature matrix is ​​obtained by capturing images of the screen using a thermal imager, such as... Figure 1 The image shown is a 4×4 box temperature distribution map. The horizontal and vertical axes on the left represent the row and column indices of the pixels (with the top left corner as the origin). The vertical resolution is 540, and the horizontal resolution is 480. The entire map represents the temperature distribution of each pixel. The values ​​on the right represent the temperatures indicated by different colors; for example, 48℃ is the yellowest part of the map, and 26℃ is the bluest part. The temperature range of the entire screen is between 26 and 48℃. The acquired images need to be preprocessed, including image tilt correction (e.g., ...). Figure 2 The diagram shows the before and after processing. Edge extraction, data interpolation, etc., are performed. Then, the middle N / 2×N / 2 modules are taken as standard blocks. Since the component arrangement of each module is the same, the average temperature of the middle N / 2×N / 2 modules is used as the temperature matrix when a single module reaches thermal equilibrium. .

[0042] Step 6. Perform single-module batch acquisition on the automated production line. Immediately after powering on each module, acquire the initial brightness matrix of 8 components. 、 、 、 、 、 、 and Then, based on the formula in step 4, perform thermal equilibrium brightness integral prediction on a single module, specifically as follows:

[0043] In the formula

[0044]

[0045] middle and Given the known quantities, based on the temperature matrix T at thermal equilibrium and the brightness in the initial state... The corresponding brightness matrix sequence is obtained. Brightness correction is performed based on the predicted values. The resulting single-module correction effects can be arbitrarily spliced ​​together without considering the screen's position. Brightness correction of LED modules based on the brightness matrix sequence at thermal equilibrium is a mature existing technology and will not be discussed further in this invention. The focus of this invention is on how to obtain the predicted brightness matrix at thermal equilibrium and how to modify the existing brightness correction method for LED displays.

[0046] Example 2

[0047] This implementation further defines Example 1, and uses specific data to further illustrate the steps in Example 1.

[0048] Step 1. Select a single LED module with a P1.25 dot pitch for the experiment, with dimensions of 135×120 (unit: number of pixels). First, use a camera and thermal imager to continuously photograph the single module to obtain the corresponding... (Temperature matrix) and (Luminosity integral matrix) The thermal imager has a resolution of 192×256.

[0049] Step 2. According to The formula performs polynomial fitting on 300 sets of brightness and temperature data.

[0050] Perform the minimization calculation, and calculate S respectively. , , , Taking the partial derivatives of and setting them equal to 0, we obtain the system of linear equations:

[0051] Complete the polynomial coefficients of the individual components.

[0052] Step 3. After switching different colors and rotating the X, Y, and Z filters, obtain 8 sets of LED brightness data. Perform 8 independent experiments according to the above steps. Note that each independent experiment must start from when the surface temperature of a single module is 20℃, and the air conditioner must not blow directly on the screen. Ensure that the ambient temperature is consistent with the surface temperature of the single module. Then, there are 8 sets of polynomial formulas:

[0053]

[0054] All fitting coefficients were obtained after calculation.

[0055] Step 4. After assembling the LED single modules with a P1.25 dot pitch in a 4x4 grid, simultaneously capture brightness and temperature data. Perform coordinate positioning, noise reduction, and grayscale integration on the brightness data to obtain a set of 135×120 brightness data points. Then, perform tilt correction, edge extraction, data interpolation, and mean calculation on the thermal imager to obtain a set of 135×120 temperature data points.

[0056] Step 5. Before the same batch of products leaves the factory, set the target brightness and color temperature. On the automated production line, collect data from individual modules in batches. After each module is plugged in, instantly collect the brightness integral matrix of 8 components. Then, based on:

[0057]

[0058] Perform thermal balance luminance integral prediction on a single module, replace the actual collected luminance integral value, and use the predicted value for chromaticity correction. The resulting single-module correction effect can be arbitrarily spliced ​​together without considering the position of the screen.

[0059] Example 3

[0060] This embodiment 3 provides an LED display screen brightness correction system, such as Figure 4 As shown, the system includes:

[0061] The data acquisition unit: Before splicing the LED display screen, the brightness matrix and corresponding temperature matrix of the red, green and blue chips of each type of LED single module constituting the LED display screen are collected under the X, Y and Z filters; for multiple LED single modules of the same type, one is selected as a representative.

[0062] The unit used for data calculation calculates the mapping relationship between the brightness matrix and the corresponding temperature matrix of each LED module based on the collected brightness matrix and temperature matrix. However, the brightness of the red chip in the LED module under the Z filter is approximately zero, so no mapping relationship is established. This results in eight identical mapping formulas for each LED module. Therefore, for each LED module, the unit calculates the mapping relationship based on the temperature matrix corresponding to the LED module when it reaches thermal equilibrium. Without requiring measurement, the predicted brightness matrix of a single LED module when it reaches thermal equilibrium is obtained. ;

[0063] Unit for brightness correction: For different models of LED modules, based on the predicted brightness matrix when the LED module reaches thermal equilibrium. Brightness correction is performed on a single LED module to obtain a brightness-corrected single LED module;

[0064] Units used for LED single-module splicing: splicing different models of LED single modules into an LED display screen.

Claims

1. A method for brightness correction of an LED display screen, characterized in that, The method is specifically as follows: Before splicing, each LED module of a certain model that makes up the LED display screen is subjected to brightness calibration. The brightness correction method involves establishing a mapping relationship between the brightness matrices acquired by the red, green, and blue chips of a single LED module under X, Y, and Z filters and the corresponding acquired temperature matrices. Since the brightness of the red chip in the single LED module is approximately zero under the Z filter, no mapping relationship is established. This results in eight identical mapping formulas, which can be used to correct any temperature matrix. To obtain the corresponding brightness matrix After establishing the mapping formula, the temperature matrix corresponding to when a single LED module reaches thermal equilibrium is used. Without requiring measurement, the predicted brightness matrix of a single LED module when it reaches thermal equilibrium is obtained. Obtain the predicted brightness matrix when a single LED module reaches thermal equilibrium. Then, based on the predicted brightness matrix when a single LED module reaches thermal equilibrium... Brightness calibration of individual LED modules; After brightness calibration of each type of LED module, the LED modules are spliced ​​together to form an LED display screen.

2. The LED display screen brightness correction method according to claim 1, characterized in that, The specific formula for the mapping relationship is as follows: ,in Represents the initial brightness matrix. … For the fitting matrix, This is the initial temperature matrix.

3. The LED display screen brightness correction method according to claim 2, characterized in that, When performing brightness calibration of an LED display screen, ensure that all LED modules of different models that make up the LED display screen are at the same initial acquisition temperature.

4. The LED display screen brightness correction method according to claim 3, characterized in that, exist middle, The value is 3.

5. The LED display screen brightness correction method according to claim 4, characterized in that, The specific solution method for the mapping relationship formula is as follows: data collection Brightness matrix of red, green and blue chips in a single LED module under X, Y and Z filters With the corresponding temperature matrix The theoretical brightness matrix is residual This indicates the deviation between the measured value and the theoretical value; Minimize, that is, for Find them separately , , , Taking the partial derivatives of and setting them equal to 0, we obtain the system of linear equations: Solving this system of equations will yield the optimal fitting coefficient matrix. , , and .

6. The LED display screen brightness correction method according to claim 5, characterized in that, The eight mapping formulas with the same representation are combined and expressed as follows: subscript , , , , , , and These correspond to the fitting relationships of the luminance and temperature matrices of the red component under the X filter, the green component under the X filter, the blue component under the X filter, the red component under the Y filter, the green component under the Y filter, the blue component under the Y filter, the green component under the Z filter, and the blue component under the Z filter, respectively.

7. The LED display screen brightness correction method according to claim 6, characterized in that, Based on the temperature matrix corresponding to when a single LED module reaches thermal equilibrium Obtain the predicted brightness matrix when a single LED module reaches thermal equilibrium. At this stage, N×N modules are constructed, and a temperature matrix is ​​obtained by capturing images of the screen using a thermal imager. The acquired images are preprocessed, including image tilt correction, edge extraction, and data interpolation. Then, the middle N / 2×N / 2 modules are selected as standard blocks. Since the component layout of each module is the same, the average temperature of the middle N / 2×N / 2 modules is used as the temperature matrix when a single module reaches thermal equilibrium. .

8. The LED display screen brightness correction method according to claim 7, characterized in that, The brightness matrix is ​​represented by grayscale values ​​captured by a CCD camera, and the temperature matrix is ​​represented by data captured by a thermal imager.

9. A brightness correction system for an LED display screen, characterized in that, The system includes: The data acquisition unit: Before splicing the LED display screen, the brightness matrix and corresponding temperature matrix of the red, green and blue chips of each type of LED single module constituting the LED display screen are collected under the X, Y and Z filters; for multiple LED single modules of the same type, one is selected as a representative. The unit used for data calculation calculates the mapping relationship between the brightness matrix and the corresponding temperature matrix of each LED module based on the collected brightness matrix and temperature matrix. However, the brightness of the red chip in the LED module under the Z filter is approximately zero, so no mapping relationship is established. This results in eight identical mapping formulas for each LED module. Therefore, for each LED module, the unit calculates the mapping relationship based on the temperature matrix corresponding to the LED module when it reaches thermal equilibrium. Without requiring measurement, the predicted brightness matrix of a single LED module when it reaches thermal equilibrium is obtained. ; Unit for brightness correction: For different models of LED modules, based on the predicted brightness matrix when the LED module reaches thermal equilibrium. Brightness correction is performed on a single LED module to obtain a brightness-corrected single LED module; Units used for LED single-module splicing: splicing different models of LED single modules into an LED display screen.

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