Method, device and system for adjusting white balance of color display screen

Abstract

The invention discloses a color display screen white balance adjusting method, device and system, and the method comprises the following steps: determining all possible combinations of R, G and B gain values, and forming a set V; a certain number of sampling points are preset in the set V, chromatic values and brightness values of the sampling points are collected, and a parameter set M is formed; constructing a linear conversion model from a gain value space to a CIE chromaticity space according to the parameter set M; based on the model, chromatic values and brightness values of all points in the V are calculated, and k optimal points are selected to form an optimal prediction set Q; and taking points in the optimal prediction set Q, writing the points into a gain register, and checking whether the white balance of the display screen is qualified or not.

Description

Technical Field

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

[0002] For color display screens, including LCD, LED, OLED, etc., after production and assembly are completed, due to certain fluctuations in the physical parameters of the components: display panel, backlight illumination component, display driving device, etc., the displayed picture will always have a certain degree of color cast. To correct the color cast, three 8-bit registers (DACs) are usually provided in the driving circuit of the color display screen to respectively control the gain values of the three primary colors of red (R), green (G), and blue (B). By writing different values to them, the gain ratios of the three colors of R, G, and B are adjusted to correct the color cast, and this adjustment operation is called white balance adjustment.

[0003] The currently common method for automatic white balance adjustment is to use the iterative search method: input the adjustment video signal into the display screen, first set the gain to 0x808080 (the gains of R, G, and B are all 1) and write it into the gain register; measure the display picture with a colorimeter to obtain the chromaticity values x, y, and the luminance value lv; analyze the color shift direction, modify the Gain value, and write it into the register again; measure again,..., repeat the above operations until x, y, and lv all meet the specification requirements.

[0004] The problems with this method are as follows: 1) It is impossible to find the optimal Gain value, and the final result is randomly distributed within the specification range, with low accuracy and a large standard deviation, resulting in a low engineering capability index Cpk value.

[0005] 2) Multiple attempts are required, and the number of adjustment times varies greatly depending on the quality characteristics of the display screen, increasing the production man-hours.

[0006] 3) Oscillation sometimes occurs, that is: the generated prediction points always jump outside the specification range and cannot fall within the specification, resulting in defective products and losses. Summary of the Invention

[0007] To achieve the above and other related purposes, the present invention discloses a method for adjusting the white balance of a color display screen, including the following steps: S1: Determine all possible combinations of the 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 to form a parameter set M; S3: Construct a linear conversion model from the gain value space to the CIE chromaticity space according to the parameter set M; S4: Based on the model, calculate the chromaticity and brightness values ​​of all points in V and select the optimal points, forming the optimal prediction set Q; S5: Take a 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.

[0008] Furthermore, the method further comprises: 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 are no qualified candidate points in the optimal prediction set Q, the candidate points of the optimal prediction set Q are added to the parameter set M, and S3-S5 are repeatedly performed until the white balance is qualified or the number of cycles reaches a preset value.

[0009] Further, constructing a linear conversion model from the gain value space to the CIE chromaticity space according to the parameter set M includes: The linear transformation model is obtained by solving the least square solution of the contradictory equations, specifically: ; Among them, the matrix is the parameter set M Coordinates, respectively, are the measured chromaticity and brightness values, matrix For sampling point Coordinates, corresponding to the R, G, B register values, insert a weight column with elements set to 1 in the first column, the matrix is the space conversion parameter to be sought; Conversion parameters The calculations include: ; ; According to the above formula, the transformation matrix is ​​obtained , used according to For each point Gain value, calculate its corresponding coordinate.

[0010] Furthermore, for each point of the set V in S1, the range of its R, G, and B gain values ​​must satisfy: ; ; ; in, , To write the gain value of the corresponding register, the value type is an 8-bit unsigned integer.

[0011] Further, the generation of the optimal prediction set Q in step S4 includes: 1) Calculate the chromaticity / luminance value of each point in according to the parameter set M and the linear transformation model;

[0012] wherein, is a matrix composed of gain values in the set , and a column of weight coefficients with element value 1 needs to be inserted into the first column, is the transformation matrix obtained in S3; is the coordinates obtained, 2) Sort all points in descending order according to the luminance value ( ). The top points are assigned luminance level 1; the middle points are assigned luminance level 2; the remaining points are assigned luminance level 3; 3) Calculate the distance between the chromaticity value of all points and the white balance center point (0.307, 0.315), and retain the points that meet the white balance specifications; 4) For the retained points, perform a multi-condition comprehensive sorting: the first priority is ascending order of luminance level, and the second priority is ascending order of chromaticity distance value; 5) Select the top points after sorting to generate the optimal prediction set Q.

[0013] On the other hand, the present invention provides a white balance adjustment device for a color display screen, including: A video signal generator for outputting a test signal to the display screen; A chromaticity meter for measuring the chromaticity value and luminance value of the display screen; A computer configured to execute the above method and control the write operation of the gain register.

[0014] Further, the chromaticity meter is arranged in a dark room environment, and the probe is in close contact with the central area of the display screen to shield environmental light interference.

[0015] On the other hand, the present invention provides a white balance adjustment system for a color display screen, including: The adjustment device as described above; A display screen for displaying a picture according to the written gain value; The computer is further configured to generate the optimal prediction set Q and dynamically optimize the adjustment parameters.

[0016] Further, the initial settings of the display screen include: The display brightness is at the maximum value, and the input test signal is a saturated white signal (RGB = 0xFFFFFF).

[0017] By adopting the above technical solution, the adjustment accuracy is high, the best white balance point of each product can be found, the standard deviation is small, and the consistency is good. The adjustment accuracy can be dynamically improved with the increase of the number of attempts until the optimal value is found. Unless the display screen is physically defective, the white balance can be adjusted to be qualified by the method of the present invention. However, the number of adjustments of the traditional method fluctuates with the product batches and is affected by the characteristics of the display screen. Sometimes, after multiple adjustments, the qualified point still cannot be found, resulting in defects. Such defects are due to the limitations of the adjustment algorithm rather than the actual defects of the 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 the adjustment accuracy and reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In combination with the accompanying drawings and with reference to the following detailed description, the above and other features and advantages of the embodiments of the present disclosure will become more apparent. The drawings are used to better understand the solution and do not constitute a limitation to the present disclosure. In the drawings, the same or similar reference numerals represent the same or similar elements, where: Figure 1 is a flowchart of the present invention; Figure 2 is a set of gain values spatial distribution diagram; Figure 3 is a comparison of the adjustment results between the method of the present invention and the current method; Figure 4 is a system configuration diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

[0020] Referring to Figure 1 , an embodiment of the present invention provides a method for adjusting the white balance of a color display screen, including the following steps: S1: Determine all possible combinations of R, G, and B gain values to form a set V.

[0021] Specifically, there are usually certain limitations on the gain values of the three primary colors R, G, and B. If the gain value > 1, color oversaturation 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 a decrease in contrast. Therefore, it is required that the gain value be as close to 1 as possible, and generally, automotive products require it to be greater than 0.9.

[0022] The value ranges of the R, G, and B gain values need to satisfy: ; ; ; In the above formula, , are the gain values written into the corresponding registers, and the numerical type is 8-bit unsigned integer.

[0023] Calculated according to the above formula, all possible combinations are 2467, and in hexadecimal representation, it is approximately: 808080~748080 (G, R, and B each account for 8 bits).

[0024] Each combination can be regarded as a point determined by the three coordinates G, R, and B, and all points together form the gain value set V.

[0025] S2: Collect the chromaticity values and brightness values of a preset number of sampling points from the set V to form a parameter set M.

[0026] Among them, in this embodiment, the number of preset sampling points is 6, and the sampling points are evenly distributed in the space of V.

[0027] S3: Construct a conversion model from the gain value space to the chromaticity space according to the parameter set M.

[0028] If the chromaticity values and brightness values of each point in V are measured , its space distribution can be plotted, such as Figure 2 , and the color of the point represents the distance of the point from the white balance center point (x = 0.307, y = 0.315).

[0029] The points are regularly arranged, and the spacing is basically uniform. Further research shows that the value change direction is indicated by the red / green / blue arrows in the figure. For example: Figure 2 the green arrow in it represents the increasing direction of the G value, which slopes from the lower left to the upper right to form layers of surfaces, and the G values of the points in each surface are the same. The G value of the top layer is 80. Similarly, the red arrow and the blue arrow represent the increasing directions of the R value and the B value.

[0030] Construct a linear conversion model from the gain value space to the chromaticity space according to the parameter set M, including: Point

[0031] Point

[0032] ; Point , then:

[0033]

[0034]

[0035]

[0036]

[0037] Let

[0038]

[0039] Substitute into the above formula to get:

[0040]

[0041] ; It can be simplified as: ; where the matrix is the coordinate of the sampling point, which are the measured chromaticity value and the luminance value . is the coordinate of the sampling point, with a weight column of elements set to 1 inserted in the first column. The matrix is the conversion parameter to be solved; Furthermore, the calculation of the conversion parameter includes: ; ; According to the above formula, the conversion matrix can be obtained, which is used to calculate the corresponding coordinate according to the gain value of each point in .

[0042] S4: Calculate the chromaticity values and luminance values of all the points in the set and select the optimal points to generate the optimal prediction set Q.

[0043] Specifically, it includes: 1) According to the parameter set M and the linear conversion model, calculate the chromaticity / luminance value of each point in

[0044]

[0045] where is the matrix composed of gain values in the set . A column of weight coefficients with element value 1 needs to be inserted in the first column. is the conversion matrix obtained in S3; is the coordinates obtained.

[0046] 2) Sort all the points in descending order of luminance value (lv). The first points are assigned luminance level 1; the middle points are assigned luminance level 2; the remaining points are assigned luminance level 3.

[0047] 3) Calculate the distance between the chromaticity values (x, y) of all the points and the white balance center point (0.307, 0.315), and retain the points that meet the white balance specifications.

[0048] 4) For the retained points, perform a multi-condition comprehensive sorting: the first priority is ascending order of luminance level, and the second priority is ascending order of chromaticity distance value.

[0049] 5) Take the first points after sorting to generate the optimal prediction set Q.

[0050] In this embodiment, .

[0051] S5: Take the points in the optimal prediction set Q in sequence, write them into the gain register of the display screen, measure the chromaticity / luminance value of the display screen, and determine whether the white balance is qualified according to the specification requirements. If the point is qualified, the white balance adjustment is successful and exit; otherwise, execute S6.

[0052] S6: Dynamically update the parameter set 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 are no qualified candidate points in the optimal prediction set Q, then the coordinates and The coordinates are added to the parameter set M, and steps S3 - S5 are repeated until a qualified candidate point is found or the number of loops reaches a preset value.

[0053] Since the number of parameter points in the parameter set M increases, the prediction accuracy of the new round will be further improved. In this embodiment, when the number of prediction loop stops is taken as 3, if a qualified value cannot be found after 3 loops, exit and report an error.

[0054] The present invention provides a new white balance adjustment method, compared with the current traditional adjustment methods: 1) High adjustment accuracy and good consistency. This method can find the best white balance point for each product, with a small standard deviation and a significant increase in the process capability index Cpk value. It is especially suitable for scenarios with high requirements for white balance adjustment accuracy, such as multi - screen splicing.

[0055] As Figure 3 , it is a comparison of the adjustment results of 110 monitors using the traditional method and the method of the present invention respectively. The green dashed - line box is the specification value range area, the blue dots are the adjustment results of the method of the present invention, concentrated near the white balance center point. The gray dots are the results obtained by the traditional method, randomly distributed within the specification area, with poor consistency. Compared with the old method, the Cpk value of the method of the present invention is increased from 0.64 (D) to 2.61 (A+).

[0056] 2) Reduce the defect rate. The number of adjustments of the traditional method varies with the fluctuation of product quality characteristics and sometimes even oscillates, that is: the generated prediction points always jump outside the specification range and cannot fall within the specification, resulting in defective products. This kind of defect is due to the limitation of the adjustment algorithm rather than the real defect of the display screen. The method of the present invention can dynamically improve the adjustment accuracy as the number of attempts increases until the optimal value is found, completely eliminating the defects caused by the adjustment algorithm.

[0057] 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 process capability index Cpk, and reducing the defect rate.

[0058] On the other hand, the present invention provides a white balance adjustment device for a color display screen, including: A video signal generator for outputting a test signal to the display screen; A colorimeter for measuring the displayed image of the display screen to obtain chromaticity values and luminance values ; the colorimeter probe is vertically placed in the center of the display screen, and the rubber light - shielding cover at the front end of the probe is in close contact with the display screen.

[0059] A computer configured to execute the above - mentioned adjustment method and control the write operation of the gain register, control the colorimeter to perform measurements, etc.

[0060] To avoid interference from ambient scattered light in the measurement, the display screen and the chromometer probe need to be placed in a darkroom, and chromaticity measurement is carried out in a completely dark environment.

[0061] As Figure 4 shown, in a third aspect, the present invention provides a white balance adjustment system for a color display screen, including: The adjustment device as described above; A display screen for displaying a picture according to the written gain value; The computer is also used to generate an optimal prediction set Q and dynamically optimize the adjustment parameters.

[0062] As described above, when adjusting the white balance, in addition to the steps S1 to S6 above, it also includes: S0: Before the adjustment starts, the display screen needs to be initially set: 1) Set the display brightness of the display screen to the maximum value; 2) The input test signal is a saturated white signal (RGB = 0xFFFFFF).

[0063] The display screen works (ages) for 1 minute under the above conditions to make the display panel, drive circuit, etc. reach a steady state, facilitating subsequent chromaticity / brightness measurement.

[0064] Those skilled in the art of this technical field can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined.

[0065] For the method embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the embodiments of the present invention are not limited by the described action sequence, because according to the embodiments of the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily essential for the embodiments of the present invention.

[0066] From the description of the above embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 brightness values, and form a parameter set M; S3: construct a linear conversion model from the gain value space to the CIE chromaticity space according to 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, comprising: The linear transformation model is obtained by solving the least square solution of the contradictory equations, specifically: ; Among them, the matrix is the parameter set M Coordinates, respectively, are the measured chromaticity and brightness values, matrix For sampling point Coordinates, corresponding to the R, G, B register values, insert a weight column with elements set to 1 in the first column, the matrix is the space conversion parameter to be sought; Conversion parameters The calculations include: ； ； According to the above formula, the transformation matrix is ​​obtained , used according to For each point Gain value, calculate its corresponding coordinate; S4: Based on the model, calculate the chromaticity and brightness values ​​of all points in V and select the optimal points, forming 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 are no qualified candidate points in the optimal prediction set Q, the candidate points of the optimal prediction set Q are added to the parameter set M, and S3-S5 are repeatedly performed 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 range of R, G, and B gain values ​​must meet the following requirements: ； ； ； in, , To write the gain value of the corresponding register, 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: According to the parameter set M and the linear transformation model, we can calculate The chromaticity / brightness value of each point in; ； in, For collection In the matrix composed of gain values, a weight coefficient column needs to be inserted in the first column, and the element value is 1. is the transformation matrix obtained for S3; To seek coordinate, Sort all points by brightness value (lv) from high to low. The points in the middle are assigned brightness level 1; The points are assigned brightness level 2; 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 keep the points that meet the white balance specifications; For the retained points, a comprehensive sorting of multiple conditions 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 sorted first points to generate the optimal prediction set Q.

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

5. A color display screen white balance adjustment system, characterized in that: include: The adjustment device as claimed in claim 4; A display screen, used for displaying images according to the written gain values; 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 (RGB=0xFFFFFF).

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