A method and apparatus for joint correction of display screen viewing angle and camera vignetting

Abstract

This application relates to a method and apparatus for joint correction of display screen viewing angle and camera vignetting, belonging to the field of display screen brightness measurement technology. The method includes the following steps: acquiring grayscale images of the same first display screen from different preset viewing angles using the same camera to obtain a measurement brightness matrix of multiple original images; calculating the coordinates of each pixel in each original image and the shooting angle parameters through pixel positioning to obtain a corresponding shooting parameter matrix; obtaining a screen viewing angle model and a camera vignetting model based on the measurement brightness matrix and the shooting parameter matrix; and calibrating the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model. This application simplifies the calibration process of the screen viewing angle model and the camera vignetting model, reducing the dependence on specific optical instruments during calibration, thus meeting the requirements for joint correction of display screen viewing angle and camera vignetting.

Description

Technical Field

[0001] This application relates to the field of display screen brightness measurement technology, specifically to a method and apparatus for joint correction of display screen viewing angle and camera vignetting. Background Technology

[0002] Currently, screen viewing angle correction and camera vignetting correction in display brightness measurement are calibrated and corrected separately. Generally, camera vignetting model calibration is performed first, followed by screen viewing angle model calibration. Furthermore, both screen viewing angle model calibration and camera vignetting model calibration rely on specific optical instruments and can only be performed in a laboratory. Camera vignetting model calibration requires an integrating sphere, and there are specific requirements for the size of the integrating sphere and the light source; screen viewing angle measurement relies on a conical lens or a special mechanical structure to measure the viewing angle.

[0003] For LCD screens, due to the different viewing angle characteristics of high and low grayscale levels, obtaining the corresponding model based on the traditional methods mentioned above would require a very large amount of computation.

[0004] Therefore, there is an urgent need for a technology that combines display viewing angle and camera vignetting correction to address the aforementioned technical problems. Summary of the Invention

[0005] This application provides a method and apparatus for joint correction of display screen viewing angle and camera vignetting, which simplifies the calibration process of the display screen viewing angle model and the camera vignetting model, reduces the dependence on specific optical instruments during the calibration process, and meets the requirements for joint correction of display screen viewing angle and camera vignetting.

[0006] In a first aspect, a method for jointly correcting display screen viewing angle and camera vignetting, the method comprising the following steps:

[0007] The same camera is used to capture grayscale images of the same first display screen from different preset angles to obtain the measurement brightness matrix of multiple original images;

[0008] By using pixel localization, the coordinates of each pixel in each original image and the shooting angle parameters are calculated to obtain the corresponding shooting parameter matrix;

[0009] Based on the measured brightness matrix and the shooting parameter matrix, the screen viewing angle model and the camera vignetting model are obtained;

[0010] Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated. The first display screen and the display screen under test are of the same type.

[0011] Specifically, the calculation of the coordinates of each pixel in each original image and the shooting angle parameters includes the following steps:

[0012] Based on the working distance of the camera during acquisition and the pixel pitch of the screen, the coordinates of each pixel in each original image and the shooting angle parameters are obtained through pixel positioning.

[0013] Furthermore, before calibrating the brightness of the display screen under test, the method further includes a pre-calibration step, which includes the following steps:

[0014] The brightness of the display screen under test is calibrated for the first time using a preset display screen viewing angle model and a camera vignetting model.

[0015] Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated a second time.

[0016] The accuracy of the first calibration result is evaluated based on the second calibration result.

[0017] Furthermore, the method also includes the following steps:

[0018] When the accuracy is lower than the preset accuracy threshold, the brightness of the display screen under test is calibrated based on the screen viewing angle model, the camera vignetting model, the preset display screen viewing angle model, and the camera vignetting model.

[0019] Specifically, the process of acquiring grayscale images of the same first display screen using the same camera from different preset perspectives includes the following steps:

[0020] Multiple grayscale images of the first display screen are captured vertically from different positions directly above the first display screen at the same shooting distance using the same camera. Each grayscale image includes the entire image of the display screen.

[0021] Preferably, the different locations include at least:

[0022] The display screen is located at the top left, top right, bottom left, bottom right, and center.

[0023] Specifically, the process of acquiring grayscale images of the same first display screen using the same camera from different preset perspectives includes the following steps:

[0024] Using the same camera, images of different gray levels under R, G, and B images on the same first display screen are captured from different preset angles.

[0025] Secondly, this application provides a device for joint correction of display screen viewing angle and camera vignetting, the device comprising:

[0026] The image acquisition module is used to acquire grayscale images of the same first display screen from different preset angles to obtain a measurement brightness matrix of multiple original images;

[0027] The parameter extraction module is used to calculate the coordinates of each pixel in each original image and the shooting angle parameters through pixel positioning, and obtain the corresponding shooting parameter matrix.

[0028] The model acquisition module is used to obtain the screen viewing angle model and the camera vignetting model based on the measured brightness matrix and the shooting parameter matrix.

[0029] A brightness calibration module is used to calibrate the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model. The first display screen and the display screen under test are of the same type.

[0030] Furthermore, the parameter extraction module is also used to obtain the coordinates of each pixel in each original image and the shooting angle parameters by pixel positioning based on the working distance of the camera during acquisition and the pixel spacing of the screen.

[0031] Furthermore, the device also includes:

[0032] The pre-calibration module is used to perform the first calibration of the brightness of the display screen under test using a preset display screen viewing angle model and a camera vignetting model.

[0033] The pre-calibration module is also used to perform a second calibration of the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model.

[0034] The pre-calibration module is also used to evaluate the accuracy of the first calibration result based on the second calibration result.

[0035] The beneficial effects of the technical solution provided in this application include:

[0036] This application simplifies the calibration process of the screen viewing angle model and the camera vignetting model, and reduces the dependence on specific optical instruments during the calibration process, so as to meet the joint correction requirements of the display screen viewing angle and the camera vignetting. Attached Figure Description

[0037] Terminology Explanation:

[0038] DeMura: The process of compensating for Mura defects;

[0039] Mura: uneven;

[0040] LCD: Liquid Crystal Display;

[0041] OLED: Organic Light-Emitting Diodes;

[0042] FFC: Flat-Field Correction;

[0043] PPI: Pixels Per Inch, a unit of pixel density, representing the distance between pixels.

[0044] DPI: Dots Per Inch;

[0045] RGB: RGB Color Mode.

[0046] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating the steps of the method for jointly correcting display screen viewing angle and camera vignetting provided in the embodiments of this application;

[0048] Figure 2 This is a schematic diagram showing the orientation of the camera and display screen during image acquisition in the joint correction method for display screen viewing angle and camera vignetting provided in the embodiments of this application.

[0049] Figure 3 This is a structural block diagram of the display screen viewing angle and camera vignetting correction device provided in the embodiments of this application. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] The embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0052] This application provides a method and apparatus for joint correction of display screen viewing angle and camera vignetting, which simplifies the calibration process of the display screen viewing angle model and camera vignetting model, reduces the dependence on specific optical instruments during the calibration process, and meets the requirements for joint correction of display screen viewing angle and camera vignetting.

[0053] To achieve the aforementioned technical effects, the overall concept of this application is as follows:

[0054] A method for joint correction of display screen viewing angle and camera vignetting, the method comprising the following steps:

[0055] S1. Using the same camera to capture grayscale images of the same first display screen from different preset angles, a measurement brightness matrix of multiple original images is obtained.

[0056] S2. Through pixel positioning, calculate the coordinates of each pixel in each original image and the shooting angle parameters to obtain the corresponding shooting parameter matrix;

[0057] S3. Based on the measured brightness matrix and the shooting parameter matrix, obtain the screen viewing angle model and the camera vignetting model;

[0058] S4. Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated. The first display screen and the display screen under test are of the same type.

[0059] The embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0060] Firstly, see [the following] Figures 1-2 As shown in the figure, this application provides a method for joint correction of display screen viewing angle and camera vignetting, the method including the following steps:

[0061] S1. Using the same camera to capture grayscale images of the same first display screen from different preset angles, a measurement brightness matrix of multiple original images is obtained.

[0062] S2. Through pixel positioning, calculate the coordinates of each pixel in each original image and the shooting angle parameters to obtain the corresponding shooting parameter matrix;

[0063] S3. Based on the measured brightness matrix and the shooting parameter matrix, obtain the screen viewing angle model and the camera vignetting model;

[0064] S4. Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated. The first display screen and the display screen under test are of the same type.

[0065] It should be noted that in the specific operation of step S4, the brightness calibration is based on the first brightness correction model formula.

[0066] The formula for the first brightness correction model is: B(α,β,x,y)=B0*f(α,β)*g(x,y); where B is the measured brightness of the pixel on the display screen;

[0067] f(α,β) is the screen view model;

[0068] g(x,y) is the camera vignetting model;

[0069] (x,y) are the coordinates of the image formed by the pixels of the display screen in the image;

[0070] B0 = B(0,0,0,0) is the brightness measured by the camera when the camera is shooting from the front and the image of the pixels on the display falls on the center of the camera sensor;

[0071] (α,β): With the normal to the panel as the Z-axis, the directions of the two sides of the panel are the X-axis and Y-axis, respectively. α and β are the angles between the ray and the XZ plane and the YZ plane, respectively.

[0072] The display screen has many pixels. Because the positions of each pixel are not consistent, the angle at which the light emitted by the pixel enters the lens is different, and the final position of the light emitted by the pixel landing on the camera sensor target surface is also different. In this process, the factors affecting the brightness of the target surface pixels include:

[0073] 1. The brightness B0 of the luminous pixel itself;

[0074] 2. The angle (α,β) at which the light emitted by the light-emitting pixel is received by the camera is called the viewing angle characteristic f(α,β) of the screen.

[0075] 3. The position (x, y) of the light falling on the target surface; this influencing factor is called the vignetting characteristic of the camera, g(x, y).

[0076] In practice, the following process is included:

[0077] First, use a camera to photograph the same display screen from N (N>=2) different angles, and make the image of the screen fall on different positions of the camera sensor target to obtain multiple raw images;

[0078] Then, the measured brightness of each pixel is extracted using an image processing algorithm to obtain N measured brightness matrices B;

[0079] Furthermore, the coordinates and angle parameters α, β, x, y of each pixel in the original image are calculated through pixel positioning, and this matrix is ​​denoted as the shooting parameter matrix. Since there are N original images, there are also N shooting parameter matrices.

[0080] Then, model fitting is performed to derive the calibration model parameters f(α,β) and g(x,y);

[0081] Finally, based on the first brightness correction model formula, the brightness of the original image is calibrated, that is:

[0082] The technical solutions of this application are mainly applied to the fields of quality control and Mura defect compensation of display panels;

[0083] In the existing technology, the viewing angle characteristics of the display screen are the most influential factor among the sources of error in screen brightness measurement;

[0084] In OLED DeMura, viewing angle can cause errors such as uneven global brightness or global color shift.

[0085] In LCD DeMura, viewing angles can cause uneven global brightness, global color shift, and poor low grayscale edge repair. Furthermore, on large-size screens, the working distance requirement may be too large.

[0086] In Mini LED, viewing angle can cause uneven global brightness and color shift. Single-block repair can result in uneven splicing at the splicing points after splicing. Furthermore, in large-size splicing screens, there may be situations where the working distance requirement is too large.

[0087] Currently, screen viewing angle correction and camera vignetting correction are calibrated and corrected separately in the process of measuring screen brightness. Generally, the camera vignetting model is calibrated first, and then the screen viewing angle model is calibrated.

[0088] Moreover, the calibration of the screen viewing angle model and the camera vignetting model both rely on specific optical instruments and can only be completed in the laboratory.

[0089] Camera vignetting model calibration relies on an integrating sphere, and there are certain requirements for the size of the integrating sphere and the light source;

[0090] Screen viewing angle measurement relies on conical lenses or special mechanical structures to measure the viewing angle;

[0091] For LCD screens, due to the different viewing angle characteristics of high and low grayscale levels, obtaining the corresponding model based on the traditional methods mentioned above would require a very large amount of computation.

[0092] The technical solution in this application simplifies the calibration process of the screen viewing angle model and the camera vignetting model, reduces the dependence on specific optical instruments during the calibration process, and meets the joint correction requirements of the display screen viewing angle and the camera vignetting.

[0093] The embodiments of this application solve the problem of difficulty in calibrating the viewpoint model on the production line;

[0094] By simply taking pictures of the display screen with a camera, both the screen's viewing angle model and the camera's vignetting model can be simultaneously fitted. This eliminates the need to rely on expensive optical instruments to repeatedly measure the camera's vignetting and the display screen's viewing angle separately, significantly reducing instrument and personnel training costs. It also reduces operational steps, minimizes sources of error, and indirectly improves accuracy.

[0095] Based on the technical solutions of the embodiments of this application, this application includes a calibration process and a correction process in actual operation.

[0096] First, the calibration process involves obtaining the viewpoint model using model fitting, i.e., obtaining the screen viewpoint model and the camera vignetting model, including the following steps:

[0097] 1. Use a single camera to capture images of various gray levels of the same screen from multiple angles.

[0098] 2. Use the DeMura algorithm to extract the brightness data and pixel coordinates of the screen from multiple viewing angles, with each viewing angle corresponding to a set.

[0099] 3. Calculate the viewing angle model of the screen using calibration tools:

[0100] (1) Input data is as follows:

[0101] a. Brightness data files from various viewing angles;

[0102] b. Working distance during calibration;

[0103] c. Screen PPI, i.e., pixel pitch.

[0104] (2) The output data is as follows:

[0105] a) Screen viewpoint model file;

[0106] b. Camera vignetting model file.

[0107] It should be noted that the screen viewing angle model file and the camera vignetting model file include not only the corresponding screen viewing angle model or the camera vignetting model, but also some basic information about the display screen and optical imaging system, such as: screen size, resolution, DPI, camera sensor pixel size, and lens focal length.

[0108] Second, brightness correction includes the following procedures:

[0109] The DeMura algorithm and luminance / chromaticity calculation method are integrated to obtain the viewing angle correction algorithm module. It only needs to load the screen viewing angle model file of the corresponding display and the camera vignetting model file to support the corresponding viewing angle correction function and perform calibration.

[0110] It should be noted that when acquiring images, they can correspond to the image acquisition pattern of DeMura, and dense sampling can be performed if conditions permit.

[0111] For example: R16, G16, B16, R25, G25, B25, R32, G32, B32, R48, G48, B48, R96, G96, B96, R128, G128, B128, R225, G225, B225, R255, G255, B255;

[0112] The R, G, and B mentioned above are the three color channels in RGB. The values ​​are the gray levels that the screen illuminates. Generally, an 8-bit screen has 0 to 255 gray levels to display different brightness. Since the viewing angle characteristics of some screen types change with gray levels, it is necessary to measure the pixel brightness of different gray levels.

[0113] In addition, the following points should be noted when acquiring images:

[0114] Images need to be captured from the display screen from at least two different preset viewing angles, and the preset viewing angles need to cover as large an area as possible to ensure the maximum viewing angle that may occur during the coverage correction process.

[0115] The working distance for different preset angles must be kept consistent, that is: the camera can only move in a plane parallel to the screen.

[0116] Different preset viewing angles refer to changing the relative position of the display screen and the camera (moving the screen or moving the camera). Each time an image is captured, the camera captures the entire screen of the display screen.

[0117] One preferred image acquisition method is to keep the camera as perpendicular to the display screen as possible, maintain a consistent working distance, and place the display screen at the five positions corresponding to the camera's field of view when measuring brightness data at five different preset viewing angles.

[0118] Specifically, the original image corresponding to the preset viewing angle includes the entire display area of ​​the display screen.

[0119] Specifically, the camera shooting distances corresponding to the preset viewing angles are the same.

[0120] Specifically, when the camera captures images of the display screen from different preset angles, the camera is perpendicular to the display screen.

[0121] Specifically, the process of obtaining the screen viewing angle model and the camera vignetting model based on the measured brightness matrix and the shooting parameter matrix includes the following steps:

[0122] Based on the shooting parameter matrix, the measured brightness of each pixel, the camera shooting distance, and the screen PPI, the screen viewing angle model and the camera vignetting model are simulated and obtained.

[0123] Specifically, the calculation of the coordinates of each pixel in each original image and the shooting angle parameters includes the following steps:

[0124] Based on the working distance of the camera during acquisition and the pixel pitch of the screen, the coordinates of each pixel in each original image and the shooting angle parameters are obtained through pixel positioning.

[0125] Furthermore, before calibrating the brightness of the display screen under test, the method further includes a pre-calibration step, which includes the following steps:

[0126] The brightness of the display screen under test is calibrated for the first time using a preset display screen viewing angle model and a camera vignetting model.

[0127] Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated a second time.

[0128] The accuracy of the first calibration result is evaluated based on the second calibration result.

[0129] Furthermore, the method also includes the following steps:

[0130] When the accuracy is lower than the preset accuracy threshold, the brightness of the display screen under test is calibrated based on the screen viewing angle model, the camera vignetting model, the preset display screen viewing angle model, and the camera vignetting model.

[0131] Specifically, the process of acquiring grayscale images of the same first display screen using the same camera from different preset perspectives includes the following steps:

[0132] Multiple grayscale images of the first display screen are captured vertically from different positions directly above the first display screen at the same shooting distance using the same camera. Each grayscale image includes the entire image of the display screen.

[0133] Preferably, the different locations include at least:

[0134] The display screen is located at the top left, top right, bottom left, bottom right, and center.

[0135] Specifically, the process of acquiring grayscale images of the same first display screen using the same camera from different preset perspectives includes the following steps:

[0136] Using the same camera, images of different gray levels under R, G, and B images on the same first display screen are captured from different preset angles.

[0137] Based on the above technical solution, the embodiments of this application, in specific implementation, also include the following operation process:

[0138] The first step is to obtain a pre-calibrated screen view preset model and a camera vignetting preset model; among them,

[0139] The screen viewing angle preset model and the camera vignetting preset model are usually calibrated using traditional methods. For example, the viewing angle model of a batch of screens of the same type is measured by special optical instruments and the average is recorded as f1(α,β). The camera vignetting model can be obtained in the same way and recorded as g1(x,y).

[0140] Screen view preset models and camera vignetting preset models are usually available at the factory.

[0141] The second step is to use the above joint calibration method to obtain the parameters of the screen view model and the camera vignetting model through model fitting, which are denoted as f2(α,β) and g2(x,y) respectively.

[0142] The third step is to evaluate the accuracy of the pre-screen viewpoint model and the pre-camera vignetting model using the results of the screen viewpoint model and the camera vignetting model.

[0143] When the accuracy of the screen viewpoint preset model and the camera vignetting preset model is low, the pre-calibrated model is calibrated using the jointly calibrated model; among them,

[0144] The calibration at this point is based on the second brightness correction model formula, which is as follows:

[0145]

[0146] In summary, the technical solution of this application embodiment has the following advantages:

[0147] 1) A single calibration operation can calculate the screen view model and the camera vignetting model, reducing operation steps, thereby reducing environmental interference and improving productivity;

[0148] 2) The calibration process requires only a camera and a display screen and does not rely on additional optical instruments, which greatly reduces the cost of manpower and materials, and enables the calibration work to be transferred from the laboratory to the end production line.

[0149] 3) Since the calibration and correction processes are based on the same working environment and display screen, the spectral deviation is small, which can greatly reduce the error caused by spectral deviation compared to laboratory calibration.

[0150] It should be noted that the step numbers in the embodiments of this application do not limit the order of operations in the technical solution of this application.

[0151] Secondly, see Figure 3 As shown, based on the technology of the combined correction method for display viewing angle and camera vignetting mentioned in the first aspect, this application provides a combined correction device for display viewing angle and camera vignetting, which includes:

[0152] The image acquisition module is used to acquire grayscale images of the same first display screen from different preset angles to obtain a measurement brightness matrix of multiple original images;

[0153] The parameter extraction module is used to calculate the coordinates of each pixel in each original image and the shooting angle parameters through pixel positioning, and obtain the corresponding shooting parameter matrix.

[0154] The model acquisition module is used to obtain the screen viewing angle model and the camera vignetting model based on the measured brightness matrix and the shooting parameter matrix.

[0155] A brightness calibration module is used to calibrate the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model. The first display screen and the display screen under test are of the same type.

[0156] It should be noted that in the specific operation of step S4, the brightness calibration is based on the first brightness correction model formula.

[0157] The formula for the first brightness correction model is: B(α,β,x,y)=B0*f(α,β)*g(x,y); where B is the measured brightness of the pixel on the display screen;

[0158] f(α,β) is the screen view model;

[0159] g(x,y) is the camera vignetting model;

[0160] (x,y) are the coordinates of the image formed by the pixels of the display screen in the image;

[0161] B0 = B(0,0,0,0) is the brightness measured by the camera when the camera is shooting from the front and the image of the pixels on the display falls on the center of the camera sensor;

[0162] (α,β): With the normal to the panel as the Z-axis, the directions of the two sides of the panel are the X-axis and Y-axis, respectively. α and β are the angles between the ray and the XZ plane and the YZ plane, respectively.

[0163] The display screen has many pixels. Because the positions of each pixel are not consistent, the angle at which the light emitted by the pixel enters the lens is different, and the final position of the light emitted by the pixel landing on the camera sensor target surface is also different. In this process, the factors affecting the brightness of the target surface pixels include:

[0164] 1. The brightness B0 of the luminous pixel itself;

[0165] 2. The angle (α,β) at which the light emitted by the light-emitting pixel is received by the camera is called the viewing angle characteristic f(α,β) of the screen.

[0166] 3. The position (x, y) of the light falling on the target surface; this influencing factor is called the vignetting characteristic of the camera, g(x, y).

[0167] In practice, the following process is included:

[0168] First, use a camera to photograph the same display screen from N (N>=2) different angles, and make the image of the screen fall on different positions of the camera sensor target to obtain multiple raw images;

[0169] Then, the measured brightness of each pixel is extracted using an image processing algorithm to obtain N measured brightness matrices B;

[0170] Furthermore, the coordinates and angle parameters α, β, x, y of each pixel in the original image are calculated through pixel positioning, and this matrix is ​​denoted as the shooting parameter matrix. Since there are N original images, there are also N shooting parameter matrices.

[0171] Then, model fitting is performed to derive the calibration model parameters f(α,β) and g(x,y);

[0172] Finally, based on the first brightness correction model formula, the brightness of the original image is calibrated, that is:

[0173] The technical solutions of this application are mainly applied to the fields of quality control and Mura defect compensation of display panels;

[0174] In the existing technology, the viewing angle characteristics of the display screen are the most influential factor among the sources of error in screen brightness measurement;

[0175] In OLED DeMura, viewing angle can cause errors such as uneven global brightness or global color shift.

[0176] In LCD DeMura, viewing angles can cause uneven global brightness, global color shift, and poor low grayscale edge repair. Furthermore, on large-size screens, the working distance requirement may be too large.

[0177] In Mini LED, viewing angle can cause uneven global brightness and color shift. Single-block repair can result in uneven splicing at the splicing points after splicing. Furthermore, in large-size splicing screens, there may be situations where the working distance requirement is too large.

[0178] Currently, screen viewing angle correction and camera vignetting correction are calibrated and corrected separately in the process of measuring screen brightness. Generally, the camera vignetting model is calibrated first, and then the screen viewing angle model is calibrated.

[0179] Moreover, the calibration of the screen viewing angle model and the camera vignetting model both rely on specific optical instruments and can only be completed in the laboratory.

[0180] Camera vignetting model calibration relies on an integrating sphere, and there are certain requirements for the size of the integrating sphere and the light source;

[0181] Screen viewing angle measurement relies on conical lenses or special mechanical structures to measure the viewing angle;

[0182] For LCD screens, due to the different viewing angle characteristics of high and low grayscale levels, obtaining the corresponding model based on the traditional methods mentioned above would require a very large amount of computation.

[0183] The technical solution in this application simplifies the calibration process of the screen viewing angle model and the camera vignetting model, reduces the dependence on specific optical instruments during the calibration process, and meets the joint correction requirements of the display screen viewing angle and the camera vignetting.

[0184] The embodiments of this application solve the problem of difficulty in calibrating the viewpoint model on the production line;

[0185] By simply taking pictures of the display screen with a camera, both the screen's viewing angle model and the camera's vignetting model can be simultaneously fitted. This eliminates the need to rely on expensive optical instruments to repeatedly measure the camera's vignetting and the display screen's viewing angle separately, significantly reducing instrument and personnel training costs. It also reduces operational steps, minimizes sources of error, and indirectly improves accuracy.

[0186] Based on the technical solutions of the embodiments of this application, this application includes a calibration process and a correction process in actual operation.

[0187] First, the calibration process involves obtaining the viewpoint model using model fitting, i.e., obtaining the screen viewpoint model and the camera vignetting model, including the following steps:

[0188] 1. Use a single camera to capture images of various gray levels of the same screen from multiple angles.

[0189] 2. Use the DeMura algorithm to extract the brightness data and pixel coordinates of the screen from multiple viewing angles, with each viewing angle corresponding to a set.

[0190] 3. Calculate the viewing angle model of the screen using calibration tools:

[0191] (1) Input data is as follows:

[0192] a. Brightness data files from various viewing angles;

[0193] b. Working distance during calibration;

[0194] c. Screen PPI, i.e., pixel pitch.

[0195] (2) The output data is as follows:

[0196] a) Screen viewpoint model file;

[0197] b. Camera vignetting model file.

[0198] It should be noted that the screen viewing angle model file and the camera vignetting model file include not only the corresponding screen viewing angle model or the camera vignetting model, but also some basic information about the display screen and optical imaging system, such as: screen size, resolution, DPI, camera sensor pixel size, and lens focal length.

[0199] Second, brightness correction includes the following procedures:

[0200] The DeMura algorithm and luminance / chromaticity calculation method are integrated to obtain the viewing angle correction algorithm module. It only needs to load the screen viewing angle model file of the corresponding display and the camera vignetting model file to support the corresponding viewing angle correction function and perform calibration.

[0201] It should be noted that when acquiring images, they can correspond to the image acquisition pattern of DeMura, and dense sampling can be performed if conditions permit.

[0202] For example: R16, G16, B16, R25, G25, B25, R32, G32, B32, R48, G48, B48, R96, G96, B96, R128, G128, B128, R225, G225, B225, R255, G255, B255;

[0203] The R, G, and B mentioned above are the three color channels in RGB. The values ​​are the gray levels that the screen illuminates. Generally, an 8-bit screen has 0 to 255 gray levels to display different brightness. Since the viewing angle characteristics of some screen types change with gray levels, it is necessary to measure the pixel brightness of different gray levels.

[0204] In addition, the following points should be noted when acquiring images:

[0205] Images need to be captured from the display screen from at least two different preset viewing angles, and the preset viewing angles need to cover as large an area as possible to ensure the maximum viewing angle that may occur during the coverage correction process.

[0206] The working distance for different preset angles must be kept consistent, that is: the camera can only move in a plane parallel to the screen.

[0207] Different preset viewing angles refer to changing the relative position of the display screen and the camera (moving the screen or moving the camera). Each time an image is captured, the camera captures the entire screen of the display screen.

[0208] One preferred image acquisition method is to keep the camera as perpendicular to the display screen as possible, maintain a consistent working distance, and place the display screen at the five positions corresponding to the camera's field of view when measuring brightness data at five different preset viewing angles.

[0209] Specifically, the original image corresponding to the preset viewing angle includes the entire display area of ​​the display screen.

[0210] Specifically, the camera shooting distances corresponding to the preset viewing angles are the same.

[0211] Specifically, when the camera captures images of the display screen from different preset angles, the camera is perpendicular to the display screen.

[0212] Furthermore, the parameter extraction module is also used to obtain the coordinates of each pixel in each original image and the shooting angle parameters by pixel positioning based on the working distance of the camera during acquisition and the pixel spacing of the screen.

[0213] Furthermore, the device also includes:

[0214] The pre-calibration module is used to perform the first calibration of the brightness of the display screen under test using a preset display screen viewing angle model and a camera vignetting model.

[0215] The pre-calibration module is also used to perform a second calibration of the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model.

[0216] The pre-calibration module is also used to evaluate the accuracy of the first calibration result based on the second calibration result.

[0217] Furthermore, the brightness calibration module is also used to calibrate the brightness of the display screen under test based on the screen viewing angle model, the camera vignetting model, the preset display screen viewing angle model, and the camera vignetting model when the accuracy is lower than a preset accuracy threshold.

[0218] Specifically, the image acquisition module is used to vertically acquire multiple grayscale images of the first display screen from different positions directly above the first display screen at the same shooting distance using the same camera. Each grayscale image includes the overall image of the display screen.

[0219] It should be noted that the different positions include at least:

[0220] The display screen is located at the top left, top right, bottom left, bottom right, and center.

[0221] Specifically, the image acquisition module is used to capture images of different gray levels on the same first display screen under R, G, and B images from different preset angles using the same camera.

[0222] It should be noted that the technical problems, technical means and technical effects of the display screen viewing angle and camera vignetting correction device provided in this application are similar to those of the display screen viewing angle and camera vignetting correction method in principle.

[0223] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0224] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for jointly correcting display screen viewing angle and camera vignetting, characterized in that, The method includes the following steps: The same camera was used to capture grayscale images of the same first display screen from different preset angles to obtain the measurement brightness matrix of multiple original images; By using pixel localization, the coordinates of each pixel in each original image and the shooting angle parameters are calculated to obtain the corresponding shooting parameter matrix; Based on the measured brightness matrix and the shooting parameter matrix, the screen viewing angle model and the camera vignetting model are obtained; Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated. The first display screen and the display screen under test are of the same type. Before calibrating the brightness of the display screen under test, the method further includes a pre-calibration step, which includes the following steps: The brightness of the display screen under test is calibrated for the first time using a preset display screen viewing angle model and a preset camera vignetting model. Based on the screen viewing angle model and the camera vignetting model, the brightness of the display screen under test is calibrated a second time. The accuracy of the first calibration result is evaluated based on the second calibration result.

2. The method for joint correction of display screen viewing angle and camera vignetting as described in claim 1, characterized in that, The calculation of the coordinates of each pixel in each original image and the shooting angle parameters includes the following steps: Based on the working distance of the camera during acquisition and the pixel pitch of the screen, the coordinates of each pixel in each original image and the shooting angle parameters are obtained through pixel positioning.

3. The method for joint correction of display screen viewing angle and camera vignetting as described in claim 1, characterized in that, The method further includes the following steps: When the accuracy is lower than the preset accuracy threshold, the brightness of the display screen under test is calibrated based on the screen viewing angle model, the camera vignetting model, the preset display screen viewing angle model, and the camera vignetting model.

4. The method for joint correction of display screen viewing angle and camera vignetting as described in claim 1, characterized in that, The process of capturing grayscale images of the same first display screen using the same camera from different preset angles includes the following steps: Multiple grayscale images of the first display screen are captured vertically from different positions directly above the first display screen at the same shooting distance using the same camera. Each grayscale image includes the entire image of the display screen.

5. The method for joint correction of display screen viewing angle and camera vignetting as described in claim 4, characterized in that, The different locations include at least: The display screen is located at the top left, top right, bottom left, bottom right, and center.

6. The method for joint correction of display screen viewing angle and camera vignetting as described in claim 1, characterized in that, The process of capturing grayscale images of the same first display screen using the same camera from different preset angles includes the following steps: Using the same camera, images of different gray levels on the same first display screen are captured from different preset angles, showing the R, G, and B images respectively.

7. A device for combined correction of display screen viewing angle and camera vignetting, characterized in that, The device includes: The image acquisition module is used to acquire grayscale images of the same first display screen from different preset angles to obtain a measurement brightness matrix of multiple original images; The parameter extraction module is used to calculate the coordinates of each pixel in each original image and the shooting angle parameters through pixel positioning, and obtain the corresponding shooting parameter matrix. The model acquisition module is used to obtain the screen viewing angle model and the camera vignetting model based on the measured brightness matrix and the shooting parameter matrix. A brightness calibration module is used to calibrate the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model. The first display screen and the display screen under test are of the same type. The pre-calibration module is used to perform the first calibration of the brightness of the display screen under test using a preset display screen viewing angle model and a preset camera vignetting model. The pre-calibration module is also used to perform a second calibration of the brightness of the display screen under test based on the screen viewing angle model and the camera vignetting model. The pre-calibration module is also used to evaluate the accuracy of the first calibration result based on the second calibration result.

8. The display screen viewing angle and camera vignetting joint correction device as described in claim 7, characterized in that: The parameter extraction module is also used to obtain the coordinates of each pixel in each original image and the shooting angle parameters based on the working distance of the camera during acquisition and the pixel spacing of the screen through pixel positioning.

Images