A display screen chrominance correction method

Abstract

This invention relates to a display screen color calibration method. The method uses a camera equipped with a CIE1931-XYZ filter. The camera uses the Y filter to acquire display screen brightness data and performs initial brightness calibration to obtain a point-by-point initial brightness calibration coefficient matrix. This initial calibration coefficient matrix is ​​then uploaded to a receiving card. With initial brightness calibration enabled, the remaining six chromaticity components (red, green, and blue) are acquired and filtered. The point-by-point chromaticity calibration coefficient matrix is ​​calculated using the filtered chromaticity components. Multiplying the initial calibration coefficient matrix by the point-by-point chromaticity calibration coefficient matrix yields the final calibration coefficient matrix for the entire screen, which is then uploaded to the control system. This invention eliminates the blue "pockmark" phenomenon and improves display quality.

Description

Technical fields:

[0001] This invention belongs to the field of optoelectronics and information display technology, and specifically relates to a method for color calibration of a display screen. Background technology:

[0002] Due to the unique manufacturing process of LED chips, LED displays often exhibit issues like pinholes or bright / dark patches after assembly. These require point-to-point calibration technology to resolve, ensuring consistent brightness and color. Currently, the industry standard for point-to-point calibration is a CMOS or CCD camera. This camera captures light signals, converts them into electrical signals, stores them as digital images, and then uses algorithms to extract differences in LED points within the image. This allows for the calculation of point-to-point calibration coefficients, which the control system then uses to differentiate control, achieving point-to-point brightness and color correction. However, using digital cameras (CCD or CMOS) presents a problem: the presence of dark noise. Dark noise refers to noise introduced by the uncertainty of dark current, leading to distortion in the camera's data. Dark noise often increases exponentially with temperature. While adding cooling to the camera is an effective way to eliminate it, this is too costly for widespread engineering use and doesn't completely eliminate noise, leaving some areas uncorrected. Dark noise significantly impacts color correction, particularly blue correction. Since color correction is based on complementary colors, a certain amount of red and green is often added to ensure consistent blue. Due to the presence of dark noise, the XZ values ​​of the tristimulus in blue will fluctuate to some extent. This manifests as many red "pockmarks" appearing on the entire blue screen after the addition of auxiliary components. These "pockmarks" will seriously affect visual perception. Therefore, there is an urgent need for a correction method to eliminate the blue "pockmark" phenomenon after color correction. Summary of the Invention:

[0003] The technical problem to be solved by the present invention is to provide a color calibration method for a display screen that can eliminate the phenomenon of blue "pockmarks".

[0004] To solve the above technical problems, the display screen color correction method of the present invention is as follows: A camera is used to collect the relative brightness data of the Y component corresponding to each pixel at a high grayscale level on the display screen and perform point-by-point correction to obtain the initial brightness correction coefficient matrix for each pixel; at the same high grayscale level, the camera is used to collect the relative brightness data of the X and Z components corresponding to each pixel of the display screen after initial brightness correction; the average value of the relative brightness data of the Y component corresponding to each pixel is multiplied by a scaling factor k to obtain the corrected brightness data, where k is 0.75-0.85; the relative brightness data of the X and Z components corresponding to each pixel and the set corrected brightness data are used to construct the original tristimulus value matrix of each pixel; the common target matrix of each pixel is multiplied by the inverse matrix of the original tristimulus value matrix to obtain the color correction coefficient matrix of each pixel; the initial brightness correction coefficient matrix of each pixel is multiplied by the corresponding elements of the color correction coefficient matrix to obtain the final correction coefficient matrix; the final correction coefficient matrix of each pixel is used to perform point-by-point color correction on the display screen.

[0005] Furthermore, the relative brightness data of the X component and Z component corresponding to each pixel are filtered to obtain the filtered relative brightness data of the X component and Z component; the average value of the filtered relative brightness data is multiplied by the scaling factor k to obtain the corrected brightness data.

[0006] Furthermore, a camera with a CIE1931-XYZ filter was selected, and the Y filter was used to collect the relative brightness data of the Y component of each pixel at a high grayscale level on the display screen.

[0007] Furthermore, a monochrome camera can be selected, with a Y filter placed in front of its lens, to collect the relative brightness data of the Y component of each pixel at a high grayscale level on the display screen.

[0008] Furthermore, for pixel (i, j), the relative brightness data of its corresponding Y component includes the relative brightness values ​​RYij, GYij, and BYij of the corresponding Y component (red, green, and blue). The initial brightness correction coefficient matrix of this pixel is CBij = [rij, gij, bij]; rij, gij, and bij represent the red, green, and blue brightness correction coefficients of this pixel, respectively; i represents the row number of the pixel, j represents the column number of the pixel, i = 1, 2…M, j = 1, 2…N, and M and N are the total number of rows and columns of pixels on the display screen, respectively.

[0009] Furthermore, for pixel (i, j), the relative brightness data of its corresponding X component includes the relative brightness values ​​of red, green, and blue of the corresponding X component, RXij, GXij, and BXij, and the filtered relative brightness values ​​of red, green, and blue of the corresponding X component are RXdesij, GXdesij, and BXdesij.

[0010] Furthermore, for pixel (i, j), the relative brightness data of its corresponding Z component includes the relative brightness values ​​of red, green, and blue of the corresponding Z component, RZij, GZij, and BZij, and the filtered relative brightness values ​​of red, green, and blue of the corresponding Z component are RZdesij, GZdesij, and BZdesij.

[0011] Furthermore, for pixel (i, j), the relative brightness data of its corresponding Z component includes the green and blue relative brightness values ​​GZij and BZij of the corresponding Z component, and the filtered green and blue relative brightness values ​​of the corresponding Z component are GZdesij and BZdesij.

[0012] The corrected brightness data set for each pixel of the display screen includes the corrected red, green, and blue brightness values ​​RYdes, GYdes, and BYdes; RYdes = RYavg*k, GYdes = GYavg*k, BYdes = BYavg*k; RYavg, GYavg, and BYavg are the average values ​​of the red, green, and blue relative brightness values ​​of the Y component for all pixels.

[0013] The original tristimulus value matrix of the pixel (i, j) is XYZ_origij:

[0014]

[0015] The chromaticity correction coefficient matrix for pixel (i, j) is CCij;

[0016] CCij = [XYZ_tar] * [XYZ_orig]ij -1

[0017] XYZ_tar is the defined common target matrix.

[0018] Beneficial Effects: This invention uses a camera equipped with a CIE1931-XYZ filter. The Y-filter is used to acquire display screen brightness data and perform initial brightness correction to obtain a point-by-point initial brightness correction coefficient matrix. This initial correction coefficient matrix is ​​then uploaded to the receiving card. With initial brightness correction enabled, the remaining six chromaticity components (red, green, and blue) are acquired and filtered. The filtered chromaticity components are used to calculate the point-by-point chromaticity correction coefficient matrix. Multiplying the initial correction coefficient matrix by the point-by-point chromaticity correction coefficient matrix yields the final correction coefficient matrix for the entire screen, which is then uploaded to the control system, eliminating the blue "pockmark" phenomenon. While common chromaticity correction uses nine components, this invention also uses nine components without increasing acquisition time, while simultaneously improving display quality. Attached image description:

[0019] Figure 1 This is a flowchart of the present invention.

[0020] Figure 2 This is a diagram showing the white field effect of the display screen before calibration.

[0021] Figure 3 This is a diagram showing the white field effect of the display screen after color correction using the present invention. Detailed implementation method:

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the drawings, not the entire structure.

[0023] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0026] like Figure 1 As shown, the display screen color calibration method of the present invention is as follows:

[0027] Step 1: Perform full-screen brightness calibration on the display screen at a high grayscale level (generally 200-255). In this embodiment, when displaying red, green, and blue primary colors at 255 gray levels on an LED display screen, a camera with a CIE1931-XYZ filter is selected. The Y filter is used to capture the image of the LED display screen, obtaining the relative brightness values ​​of red, green, and blue for the Y component of each pixel. Initial brightness correction is then performed on the display screen to obtain the initial brightness correction coefficient matrix for each pixel (the initial brightness correction method for the display screen is a conventional method). Assuming the display screen resolution is M*N, where M and N are the total number of rows and columns of pixels on the display screen, the relative brightness values ​​of red, green, and blue for the Y component of pixel (i, j) on the display screen are represented as RYij, GYij, and BYij, respectively. The initial brightness correction coefficient matrix for this pixel is CBij = [rij, gij, bij], where rij, gij, and bij represent the initial brightness correction coefficients for red, green, and blue of the pixel, respectively. i represents the row number of the pixel, j represents the column number of the pixel, and i = 1, 2…M, j = 1, 2…N.

[0028] In this step, a monochrome CMOS camera or a CCD camera can also be used, with a Y filter set in front of its lens to capture the LED display screen image.

[0029] Step 2: The display screen control system loads and enables the initial brightness correction coefficient matrix for each pixel. The display screen displays the red, green, and blue primary color images after initial brightness correction at 255 gray levels. Images of the display screen are captured using the X and Z filters in the CIE1931-XYZ camera to obtain the relative brightness values ​​of red, green, and blue for each pixel in the X component and the relative brightness values ​​of red, green, and blue for the Z component. The relative brightness values ​​of red, green, and blue for the X component of pixel (i, j) are represented as RXij, GXij, and BXij, and the relative brightness values ​​of red, green, and blue for the Z component are represented as RZij, GZij, and BZij.

[0030] Due to the light-emitting characteristics of red LEDs, their wavelengths are mostly on the spectral lines and have a high saturation. The Z component corresponding to red can be assumed to be 0, i.e., RZij = 0. Therefore, this step only needs to collect 5 components.

[0031] Step 3: Gaussian Filtering: A Gaussian filter function is used to filter the relative red, green, and blue brightness values ​​of the X and Z components for each pixel, resulting in filtered relative red, green, and blue brightness values ​​for the corresponding X and Z components. The filtered relative red, green, and blue brightness values ​​of the X and Z components for pixel (i, j) are represented as RXdesij, GXdesij, BXdesij, RZdesij, GZdesij, BZdesij, respectively. Applying Gaussian filtering (or other filtering methods in existing technologies) to the acquired data can eliminate data fluctuations caused by camera dark noise without requiring additional cooling, saving equipment costs. Gaussian filtering is a commonly used method; other image filtering functions, such as median filtering, can also be used.

[0032] Step 4: Set the corrected brightness values: Take the average of the red, green, and blue relative brightness values ​​for the Y component of all pixels to obtain the average relative brightness values ​​of the red, green, and blue components of the display screen: RYavg, GYavg, and BYavg.

[0033]

[0034]

[0035]

[0036] The average relative brightness values ​​of red, green, and blue, RYavg, GYavg, and BYavg, are multiplied by a scaling factor k to obtain the corrected red, green, and blue brightness values ​​of each pixel on the display screen, RYdes, GYdes, and BYdes; RYdes = RYavg * k, GYdes = GYavg * k, BYdes = BYavg * k; for any primary color, the corrected brightness value of each pixel is the same.

[0037] The proportionality coefficient k is an empirical value, generally selected between 0.75 and 0.85.

[0038] Step 5: Construct the original tristimulus value matrix for each pixel using the red, green, and blue relative brightness values ​​of the corresponding X and Z components after filtering, as well as the corrected brightness values. The original tristimulus value matrix of pixel (i, j) is represented as XYZ_origij.

[0039]

[0040] Step Six: Set the Common Objective Matrix The target value matrix is ​​generally calculated based on the factory-set brightness of the three primary colors of the display screen (RtY, GtY, BtY) and the factory-required chromaticity coordinates (Rtx, Rty), (Gtx, Gty), and (Btx, Bty). The factory-required chromaticity coordinates can be set to the chromaticity coordinates of standard color gamuts such as Rec.709 and DCI-P3, or chromaticity coordinates specified by the customer.

[0041] RXtar=RtY*(Rtx / Rty), RYtar=RtY, RZtar=RtY*(1-Rtx-Rty) / Rty

[0042] GXtar=GtY*(Gtx / Gty), GYar=GtY, GZtar=GtY*(1-Gtx-Gty) / Gty

[0043] BXtar=BtY*(Rtx / Rty), BYtar=BtY, BZtar=BtY*(1-Btx-Bty) / Bty

[0044] Step 7: Calculate the chromaticity correction coefficient matrix for each pixel based on the original tristimulus value matrix XYZ_orig and the common target matrix XYZ_tar; the chromaticity correction coefficient matrix for pixel (i, j) is CCij;

[0045]

[0046] rrij is the brightness coefficient of the red light when the source signal is red;

[0047] rgij is the brightness coefficient of the green light when the source signal is red;

[0048] rbij is the brightness coefficient of the blue light when the display source signal is red;

[0049] grij is the brightness coefficient of the red light when the source signal is green;

[0050] ggij is the brightness coefficient of the green light when the source signal is green;

[0051] gbij represents the brightness coefficient of the blue light when the source signal is green;

[0052] brij represents the brightness coefficient of the red light when the source signal is blue.

[0053] bgij represents the brightness coefficient of the green light when the source signal is blue;

[0054] bbij is the brightness coefficient of the blue light when the display source signal is blue.

[0055] Step 8: Multiply each element of the initial luminance correction coefficient matrix CBij of pixel (i, j) with each element of its chrominance correction coefficient matrix CCij to obtain the final correction coefficient matrix CFij.

[0056]

[0057] Step 9: The display screen control system uploads the final correction coefficient matrix CFij for each pixel, performs differentiated control, and realizes point-by-point color correction of the display screen.

Claims

1. A method for color calibration of a display screen, characterized in that... The method is as follows: A camera is used to collect the relative brightness data of the Y component corresponding to each pixel at a high grayscale level on the display screen and perform point-by-point correction to obtain the initial brightness correction coefficient matrix for each pixel; at the same high grayscale level, the camera is used to collect the relative brightness data of the X and Z components corresponding to each pixel on the display screen after initial brightness correction; the relative brightness data of the X and Z components corresponding to each pixel are filtered to obtain filtered relative brightness data of the X and Z components; the average value of the relative brightness data of the Y component corresponding to each pixel is multiplied by a scaling factor k to obtain the corrected brightness data, where k is 0.75-0.85; the original tristimulus value matrix of each pixel is constructed using the filtered relative brightness data of the X and Z components of each pixel and the set corrected brightness data; the common target matrix of each pixel is multiplied by the inverse matrix of the original tristimulus value matrix to obtain the chromaticity correction coefficient matrix of each pixel; the initial brightness correction coefficient matrix of each pixel is multiplied by the corresponding elements of the chromaticity correction coefficient matrix to obtain the final correction coefficient matrix; the final correction coefficient matrix of each pixel is used to perform point-by-point chromaticity correction on the display screen.

2. The display screen color calibration method according to claim 1, characterized in that: Select a camera with a CIE1931-XYZ filter, and use the Y filter to collect the relative brightness data of the Y component of each pixel at a high grayscale level on the display screen.

3. The display screen color calibration method according to claim 1, characterized in that: Select a monochrome camera, set a Y filter in front of its lens, and collect the relative brightness data of the Y component of each pixel at a high grayscale level on the display screen.

4. The display screen color calibration method according to claim 1, characterized in that: For pixel (i, j), its corresponding Y component relative brightness data includes the red, green, and blue relative brightness values ​​RYij, GYij, and BYij of the corresponding Y component. The initial brightness correction coefficient matrix for this pixel is CBij=[rij, gij, bij]; rij, gij, and bij represent the red, green, and blue brightness correction coefficients of this pixel, respectively; i represents the row number of the pixel, j represents the column number of the pixel, i=1,2…M, j=1,2…N, and M and N are the total number of rows and columns of pixels on the display screen, respectively.

5. The display screen color calibration method according to claim 4, characterized in that: For pixel (i, j), the relative brightness data of its corresponding X component includes the relative brightness values ​​of red, green and blue of the corresponding X component RXij, GXij and BXij, and the filtered relative brightness values ​​of red, green and blue of the corresponding X component are RXdesij, GXdesij and BXdesij.

6. The display screen color calibration method according to claim 5, characterized in that: For pixel (i, j), the relative brightness data of its corresponding Z component includes the relative brightness values ​​of red, green and blue of the corresponding Z component, RZij, GZij and BZij, and the filtered relative brightness values ​​of red, green and blue of the corresponding Z component are RZdesij, GZdesij and BZdesij.

7. The display screen color calibration method according to claim 5, characterized in that: For pixel (i, j), the relative brightness data of its corresponding Z component includes the green and blue relative brightness values ​​GZij and BZij of the corresponding Z component, and the filtered green and blue relative brightness values ​​of the corresponding Z component are GZdesij and BZdesij.

8. The display screen color calibration method according to claim 6, characterized in that: The corrected brightness data set for each pixel of the display screen includes the corrected red, green, and blue brightness values ​​RYdes, GYdes, and BYdes; RYdes = RYavg*k, GYdes = GYavg*k, BYdes = BYavg*k; RYavg, GYavg, and BYavg are the average values ​​of the red, green, and blue relative brightness values ​​of the Y component for all pixels.

9. The display screen color calibration method according to claim 8, characterized in that: The original tristimulus value matrix of the pixel (i, j) is :

Images