A method, device and system for adjusting white balance of a color display screen

Abstract

The present invention discloses a method, device and system for adjusting the white balance of a color display screen, comprising the following steps: determining all possible combinations of R, G, and B gain values ​​to form a set V; presetting a certain number of sampling points in the set V, collecting their chromaticity values ​​and luminance values ​​to form a parameter set M; constructing a linear conversion model from a gain value space to a CIE chromaticity space based on the parameter set M; calculating the chromaticity values ​​and luminance values ​​of all points in V based on the model, selecting the optimal k points to form an optimal prediction set Q; taking points in the optimal prediction set Q, writing them into a gain register, and checking whether the white balance of the display screen is qualified.

Description

Technical Field

[0001] The present invention relates to the field of display screens, and in particular to a method, device and system for adjusting the white balance of a color display screen. Background Art

[0002] After color displays, including LCDs, LEDs, and OLEDs, are assembled, the displayed image will always have a certain degree of color cast due to fluctuations in the physical parameters of their components: display panels, backlighting components, and display drivers. To correct this color cast, the driver circuit of a color display typically includes three 8-bit registers (DACs) that control the gain of the three primary colors: red (R), green (G), and blue (B). By writing different values ​​to these registers, the gain ratio of the three colors (R, G, and B) is adjusted, thereby correcting the color cast. This adjustment is called white balance.

[0003] Currently, a common method for automatic white balance adjustment uses an iterative search method: input the adjustment video signal to the display, first set the gain Gain to 0x808080 (corresponding to the gains of R, G, and B being 1) and write it into the gain register; use a colorimeter to measure the display image to obtain the chromaticity values ​​x, y, and the luminance value lv; analyze the direction of color shift, modify the Gain value, and write it into the register again; measure again, and so on, repeating the above steps until x, y, and lv all meet the specifications.

[0004] The problems with this approach are:

[0005] 1) Unable to find the optimal Gain value, the final result is randomly distributed within the specification value range, with low precision and large standard deviation, resulting in a low engineering capability index Cpk value.

[0006] 2) Multiple attempts are required, and the number of adjustments varies greatly with the quality characteristics of the display screen, increasing production hours.

[0007] 3) Oscillation may sometimes occur, that is, the generated prediction points always jump outside the specification range and cannot fall within the specification, resulting in defective products and causing losses. Summary of the Invention

[0008] To achieve the above-mentioned and other related purposes, the present invention discloses a method for adjusting the white balance of a color display screen, comprising the following steps:

[0009] S1: Determine all possible combinations of R, G, and B gain values ​​to form a set V;

[0010] S2: Preset a certain number of sampling points in the set V, collect their chromaticity values ​​and luminance values, and form a parameter set M;

[0011] S3: Construct a linear conversion model from the gain value space to the CIE chromaticity space based on the parameter set M;

[0012] S4: Based on the model, calculate the chromaticity and brightness values ​​of all points in V, select the best k points, and form the optimal prediction set Q;

[0013] S5: Take the point in the optimal prediction set Q, write it into the gain register, and check whether the white balance of the display screen is qualified.

[0014] Furthermore, the method further comprises:

[0015] S6: Dynamically update the sampling data and iteratively optimize the linear conversion model until the adjustment result is qualified or the preset number of iterations is reached, including:

[0016] If there is no qualified candidate point in the optimal prediction set Q, the candidate point of the optimal prediction set Q is added to the parameter set M, and S3-S5 are repeatedly executed until the white balance is qualified or the number of cycles reaches a preset value.

[0017] Furthermore, constructing a linear conversion model from the gain value space to the CIE chromaticity space according to the parameter set M includes:

[0018] The linear transformation model is obtained by solving the least squares solution of the contradictory equations, specifically:

[0019] P = AX;

[0020] Among them, the matrix P is the CIE coordinates in the parameter set M, which are the measured chromaticity values ​​and luminance values ​​respectively; the matrix A is the RGB coordinates of the sampling point, where the values ​​of the 2nd, 3rd, and 4th columns of the matrix A correspond to the R, G, and B register values ​​respectively, and the 1st column is the weight column with a value of 1; the matrix X is the spatial conversion parameter to be determined;

[0021] The conversion parameter X calculation includes:

[0022] X=GP+(E n -GA)y,y∈R n ,G is the least squares generalized inverse;

[0023]

[0024] According to the above formula, the conversion matrix X is obtained, which is used to calculate the corresponding CIE coordinates according to the RGB gain value of each point in V.

[0025] Furthermore, for each point in set V in S1, the range of its R, G, and B gain values ​​must satisfy:

[0026] G gain factor: 0.9≤Gain G ≤1;

[0027] R gain factor: 0.9≤Gain R ≤1;

[0028] B gain coefficient: 0.9≤Gain B ≤1;

[0029] Among them, G, R, and B are the gain values ​​written to the corresponding registers, and the value type is an 8-bit unsigned integer.

[0030] Furthermore, generating the optimal prediction set Q in step S4 includes:

[0031] 1) Calculate the chromaticity / luminance value of each point in V based on the parameter set M and the linear transformation model;

[0032] V xyz =V rgb X

[0033] Among them, V rgb is the matrix composed of gain values ​​in the set V. It is necessary to insert a weight coefficient column in the first column with the element value 1. X is the conversion matrix obtained by S3; V xyz To obtain the CIE coordinates,

[0034] 2) Sort all points by brightness value (lv) from high to low. The first a% of points are assigned brightness level 1; the middle b% of points are assigned brightness level 2; and the remaining points are assigned brightness level 3.

[0035] 3) Calculate the distance between the chromaticity value (x, y) of all points and the white balance center point (0.307, 0.315), and retain the points that meet the white balance specifications;

[0036] 4) For the retained points, perform a comprehensive sorting based on multiple conditions: the first priority is the ascending order of brightness level, and the second priority is the ascending order of chromaticity distance value;

[0037] 5) Take the first k points after sorting and generate the optimal prediction set Q.

[0038] In another aspect, the present invention provides a device for adjusting white balance of a color display screen, comprising:

[0039] A video signal generator, used to output a test signal to the display screen;

[0040] Colorimeter, used to measure the colorimetry and brightness of the display;

[0041] A computer is configured to execute the above method and control the write operation of the gain register.

[0042] Furthermore, the colorimeter is placed in a darkroom environment, and the probe is in close contact with the central area of ​​the display screen to shield interference from ambient light.

[0043] In another aspect, the present invention provides a color display white balance adjustment system, comprising:

[0044] An adjustment device as described above;

[0045] Display screen, used to display images according to the written gain value;

[0046] The computer is also used to generate an optimal prediction set Q and dynamically optimize and adjust parameters.

[0047] Furthermore, the initial setting of the display screen includes:

[0048] The display brightness is at the maximum value, and the input test signal is a saturated white signal. When RGB=0xFFFFFF, the test signal is a saturated white signal.

[0049] By adopting the above technical solution, the adjustment accuracy is high, and the optimal white balance point for each product can be found. The standard deviation is small, the consistency is good, and the adjustment accuracy can be dynamically improved as the number of attempts increases until the optimal value is found. Unless the display screen is physically defective, the white balance can be adjusted to meet the requirements through the method of the present invention. The number of adjustments with traditional methods fluctuates with product batches and is affected by the characteristics of the display screen. Sometimes, multiple adjustments still cannot find the qualified point, resulting in a defect. This defect is due to the limitations of the adjustment algorithm rather than a real defective display screen. The white balance adjustment system of the present invention can be directly applied to the production line of color display screens, thereby improving adjustment accuracy and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The above and other features and advantages of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. The accompanying drawings are provided for a better understanding of the present solution and do not constitute a limitation of the present disclosure. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, among which:

[0051] Figure 1 is a flow chart of the present invention;

[0052] Figure 2 is the CIE1931 spatial distribution diagram of the RGB gain value set V;

[0053] Figure 3 Comparison of adjustment results between the method of the present invention and the existing method;

[0054] Figure 4 This is a system configuration diagram of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0056] Reference Figure 1 , an embodiment of the present invention provides a method for adjusting white balance of a color display screen, comprising the following steps:

[0057] S1: Determine all possible combinations of R, G, and B gain values ​​to form a set V.

[0058] Specifically, the gain values ​​of the three primary colors (R, G, and B) are generally limited. If the gain value is greater than 1, color oversaturation and distortion will occur when displaying high-brightness images. On the other hand, the smaller the gain value, the greater the brightness loss of the image, resulting in reduced contrast. Therefore, the gain value should be as close to 1 as possible, and generally greater than 0.9 for automotive products.

[0059] The value ranges of R, G, and B gain values ​​must meet the following requirements:

[0060] G gain factor: 0.9≤Gain G ≤1;

[0061] R gain factor: 0.9≤Gain R ≤1;

[0062] B gain coefficient: 0.9≤Gain B ≤1;

[0063] In the above formula, G, R, and B are the gain values ​​written to the corresponding registers, and the value type is an 8-bit unsigned integer.

[0064] According to the above formula, there are 2467 possible GRB combinations, which are approximately 808080 to 748080 in hexadecimal (G, R, and B each occupy 8 bits).

[0065] Each combination can be regarded as a point determined by the three coordinates G, R, and B, and all points together constitute the gain value set V.

[0066] S2: Collect the chromaticity values ​​and luminance values ​​of a preset number of sampling points from the set V to form a parameter set M.

[0067] In this embodiment, the number of preset sampling points is 6, and the sampling points are evenly distributed in the CIE space of V.

[0068] S3: Construct a conversion model from the gain value space to the CIE chromaticity space based on the parameter set M.

[0069] If the chromaticity and brightness values ​​(x, y, lv) of each point in V are measured, its CIE spatial distribution can be plotted, as shown in the following example: Figure 2 The color of a point indicates the distance between the point and the white balance center point (x=0.307, y=0.315).

[0070] The points are arranged regularly and the spacing is basically uniform. Further research shows that the direction of change of RGB values ​​is indicated by the red / green / blue arrows in the figure. For example: Figure 2 The green arrow in the middle indicates the direction of increasing G values, sloping from the lower left to the upper right to form layers of surfaces. Each point in each surface has the same G value. The G value of the top layer is 80. Similarly, the red and blue arrows indicate the direction of increasing R and B values.

[0071] A linear conversion model from the gain value space to the CIE chromaticity space is constructed according to the parameter set M, including:

[0072] Point P0: RGB coordinates are (r0, g0, b0), and CIE coordinates are (x0, y0, z0)

[0073] Point P: RGB coordinates are (r, g, b), CIE coordinates are (x, y, z)

[0074]

[0075] The increment of point P relative to P0 in the RGB coordinate system is (m,n,q)=(r-r0,g-g0,b-b0), then:

[0076] Let α0=x0-r0α1-g0α2-b0α3,

[0077] β0=y0-r0β1-g0β2-bβ3,

[0078] γ0=z0-r0γ1-g0γ2-bγ3, substituting into the above formula, we get:

[0079]

[0080] In order to offset the measurement error, when n sampling points p1~p n When , a contradictory set of equations is formed:

[0081]

[0082] It can be simplified as: P = AX;

[0083] Wherein, the matrix P is the CIE coordinates of the sampling points, which are the measured chromaticity values ​​(x, y) and luminance values ​​(z). A is the RGB coordinates of the sampling points, with a weight column with the first column set to 1. The matrix X is the transformation parameter to be determined;

[0084] Furthermore, the conversion parameter X calculation includes:

[0085] X=GP+(E 4×4 -GA)y,y∈R 4 ,G is the least squares generalized inverse;

[0086]

[0087] According to the above formula, the conversion matrix X can be obtained, which is used to calculate the corresponding CIE coordinates according to the RGB gain value of each point in V.

[0088] S4: Based on the linear conversion model, calculate the chromaticity values ​​and luminance values ​​of all points in the set V, select the optimal k points, and generate the optimal prediction set Q.

[0089] Specifically, they include:

[0090] 1) Based on the parameter set M and the linear transformation model, calculate the chromaticity / luminance value of each point in V.

[0091] V xyz =V rgb X

[0092] Among them, V rgb is the matrix composed of gain values ​​in the set V. It is necessary to insert a weight coefficient column in the first column with the element value 1. X is the transformation matrix obtained by S3; V xyz To obtain the CIE coordinates.

[0093] 2) Sort all points by brightness value (lv) from high to low. The first a% of points are assigned brightness level 1; the middle b% of points are assigned brightness level 2; and the remaining points are assigned brightness level 3.

[0094] 3) Calculate the distance between the chromaticity value (x, y) of all points and the white balance center point (0.307, 0.315), and retain the points that meet the white balance specifications.

[0095] 4) For the retained points, perform a comprehensive sorting based on multiple conditions: the first priority is the ascending order of brightness level, and the second priority is the ascending order of chromaticity distance value.

[0096] 5) Take the first k points after sorting and generate the optimal prediction set Q.

[0097] In this embodiment, k=5, a%=39%, b%=39%.

[0098] S5: Sequentially select points from the optimal prediction set Q, write them into the display's gain register, measure the display's chromaticity / luminance values, and determine whether the white balance meets the specifications. If the point meets the requirements, the white balance adjustment is successful and the process exits; otherwise, execute S6.

[0099] S6: Dynamically updating the parameter set data and iteratively optimizing the linear conversion model until the adjustment result is qualified or the preset number of iterations is reached, including:

[0100] If there is no qualified candidate point in the optimal prediction set Q, the RGB coordinates and CIE coordinates of the candidate point in the optimal prediction set Q are added to the parameter set M, and S3-S5 are repeated until a qualified candidate point is found or the number of cycles reaches a preset value.

[0101] Since the number of parameter points in the parameter set M increases, the prediction accuracy of the next round will be further improved. In this embodiment, when the number of prediction cycle stops is equal to 3, if a qualified value cannot be found after 3 cycles, the process exits and reports an error.

[0102] The present invention provides a new white balance adjustment method, compared with the current traditional adjustment method:

[0103] 1) High adjustment accuracy and good consistency. This method can find the optimal white balance point for each product, with a small standard deviation and significantly improved process capability index (Cpk). It is particularly suitable for scenarios such as multi-screen splicing that require high white balance adjustment accuracy.

[0104] like Figure 3 The following table compares the adjustment results of 110 monitors using the traditional method and the method of the present invention. The green dashed box indicates the specification range, and the blue dots represent the adjustment results of the method of the present invention, concentrated near the center of white balance. The gray dots represent the results obtained by the traditional method, which are randomly distributed within the specification range and have poor consistency. Compared with the traditional method, the method of the present invention improves the Cpk value from 0.64 (D) to 2.61 (A+).

[0105] 2) Reduce defective product rates. The number of adjustments made by traditional methods varies with fluctuations in product quality characteristics, sometimes even causing oscillations. This means the generated prediction points consistently jump outside the specification range and fail to fall within it, resulting in defective products. These defects are due to limitations in the adjustment algorithm rather than actual display failures. The method of the present invention dynamically improves adjustment accuracy as the number of attempts increases, until the optimal value is found, completely eliminating defects caused by the adjustment algorithm.

[0106] The white balance adjustment system of the present invention can be directly applied to the production line of color display screens, significantly improving the adjustment accuracy and the engineering capability index Cpk, and reducing the defective rate.

[0107] In another aspect, the present invention provides a device for adjusting white balance of a color display screen, comprising:

[0108] A video signal generator, used to output a test signal to the display screen;

[0109] A colorimeter is used to measure the image displayed on the display screen to obtain CIE1931 chromaticity and luminance values ​​(x, y, lv). The colorimeter probe is placed vertically in the center of the display screen, with the rubber hood at the front end of the probe in close contact with the display screen.

[0110] The computer is configured to execute the above adjustment method, control the write operation of the gain register, control the colorimeter to perform measurement, etc.

[0111] In order to avoid interference of ambient scattered light in the measurement, the display screen and colorimeter probe need to be placed in a dark room and colorimetry measurements should be performed in a completely dark environment.

[0112] like Figure 4 As shown, in a third aspect, the present invention provides a color display white balance adjustment system, comprising:

[0113] An adjustment device as described above;

[0114] Display screen, used to display images according to the written gain value;

[0115] The computer is also used to generate an optimal prediction set Q and dynamically optimize and adjust parameters.

[0116] When adjusting the white balance, in addition to the above steps S1 to S6, the following steps are also included:

[0117] S0: Before adjustment begins, the display needs to be initially set up:

[0118] 1) Set the display brightness to the maximum value;

[0119] 2) The input test signal is a saturated white signal (RGB=0xFFFFFF).

[0120] The display screen is powered on and operated (aged) for 1 minute under the above conditions to allow the display panel, drive circuit, etc. to reach a steady state, which is convenient for subsequent chromaticity / luminance measurement.

[0121] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art in the art to which the present invention pertains. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with those in the context of the prior art and, unless specifically defined, will not be interpreted in an idealized or overly formal sense.

[0122] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the embodiments of the present invention are not limited by the order of the actions described, because certain steps can be performed in other orders or simultaneously according to the embodiments of the present invention. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present invention.

[0123] Through the description of the above embodiments, it can be seen that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general-purpose hardware platform. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments of the present application or certain parts of the embodiments.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for adjusting white balance of a color display screen, characterized in that: The following steps are involved: S1: Determine all possible combinations of R, G, and B gain values ​​to form a set V; S2: Preset a certain number of sampling points in the set V, collect their chromaticity values ​​and luminance values, and form a parameter set M; S3: Construct a linear conversion model from the gain value space to the CIE chromaticity space based on the parameter set M; The linear conversion model from the gain value space to the CIE chromaticity space is constructed according to the parameter set M, including: The linear transformation model is obtained by solving the least squares solution of the contradictory equations, specifically: P = AX; Among them, the matrix P is the CIE coordinates in the parameter set M, which are the measured chromaticity values ​​and luminance values ​​respectively; the matrix A is the RGB coordinates of the sampling point, where the values ​​of the 2nd, 3rd, and 4th columns of the matrix A correspond to the R, G, and B register values ​​respectively, and the 1st column is the weight column with a value of 1; the matrix X is the spatial conversion parameter to be determined; The conversion parameter X calculation includes: X=GP+(E n -GA)y,y∈R n ,G is the least squares generalized inverse; According to the above formula, the conversion matrix X is obtained, which is used to calculate the corresponding CIE coordinates according to the RGB gain value of each point in V; S4: Based on the model, calculate the chromaticity and brightness values ​​of all points in V, select the best k points, and form the optimal prediction set Q; S5: Take the point in the optimal prediction set Q, write it into the gain register, and check whether the white balance of the display screen is qualified; S6: Dynamically update the sampling data and iteratively optimize the linear conversion model until the adjustment result is qualified or the preset number of iterations is reached, including: If there is no qualified candidate point in the optimal prediction set Q, the candidate point of the optimal prediction set Q is added to the parameter set M, and S3-S5 are repeatedly executed until the white balance is qualified or the number of cycles reaches a preset value.

2. The method according to claim 1, characterized in that The value ranges of R, G, and B gain values ​​must meet the following requirements: G gain factor: R gain factor: B gain coefficient: Among them, G, R, and B are the gain values ​​written to the corresponding registers, and the value type is an 8-bit unsigned integer.

3. The method according to claim 1, characterized in that Generating the optimal prediction set Q in step S4 includes: Calculate the chromaticity / luminance value of each point in V based on the parameter set M and the linear transformation model; V xyz =V rgb X; Among them, V rgb is the matrix composed of gain values ​​in the set V. It is necessary to insert a weight coefficient column in the first column with the element value 1. X is the conversion matrix obtained by S3; V xyz To obtain the CIE coordinates, Sort all points by brightness value from high to low. The first a% of points are assigned brightness level 1; the middle b% of points are assigned brightness level 2; and the remaining points are assigned brightness level 3. Calculate the distance between the chromaticity value (x, y) of all points and the white balance center point (0.307, 0.315), and retain the points that meet the white balance specifications; For the retained points, a comprehensive multi-condition sorting is performed: the first priority is the ascending order of brightness level, and the second priority is the ascending order of chromaticity distance value; Take the first k points after sorting and generate the optimal prediction set Q.

4. A white balance adjustment device for a color display screen, characterized in that: include: A video signal generator, used to output a test signal to the display screen; Colorimeter, used to measure the colorimetry and brightness of the display; A computer configured to execute the method according to any one of claims 1 to 3 and control a write operation of a gain register.

5. A color display white balance adjustment system, characterized in that: include: The adjustment device according to claim 4; Display screen, used to display images according to the written gain value; The computer is also used to generate an optimal prediction set Q and dynamically optimize and adjust parameters.

6. The system according to claim 5, characterized in that include: The initial setting of the display screen includes: The display brightness is at the maximum value, and the input test signal is a saturated white signal. When RGB=0xFFFFFF, the test signal is a saturated white signal.

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