Screen color uniformity detection method and device

Abstract

The present invention relates to the field of screen detection technology, and specifically to a method and device for detecting screen color uniformity, the method comprising: obtaining multiple pictures taken of a screen at multiple angles, wherein the multiple pictures are obtained by taking multiple pictures of a screen with a backlight at a fixed position; taking the grayscale value of the corresponding pixel for each picture based on the multiple pictures correspondingly obtained at multiple polarization angles; calculating the phase difference of the polarization angle of each picture based on the obtained multiple grayscale values; judging whether the polarized light of each picture is linearly polarized light or circularly polarized light based on the phase difference; and calculating whether the corresponding pixel of the picture is a point with uniform brightness based on the linear polarized light or the circular polarized light. The present application obtains pictures by fixed shooting, thereby overcoming the problem of "brightness differences of polarized light due to multiple observation angles" in screen detection.

Description

Technical Field

[0001] The present invention relates to the field of screen detection technology, and in particular to a method and device for detecting screen color uniformity. Background Art

[0002] Screen color (or brightness) uniformity means that the color of each pixel should be consistent when the screen displays the same color. The national standard divides the entire screen into 9 blocks, and the brightness difference between the colors of each block does not exceed 25% to be qualified (see the figure below). The quality requirements in actual production generally require a brightness difference of 10%, which can basically ensure the uniformity of brightness and color when observed by the human eye.

[0003] The traditional method is visual inspection, that is, the entire screen displays black, pure white, red, green, blue and other colors, and then people observe whether there are differences, so as to judge the uniformity of the screen in various color states. This method consumes a lot of vision and is easy to cause eye fatigue. For screens with high quality requirements, the precision and stability of human eye detection are problematic.

[0004] In view of the problems with human eye detection, some screen inspections currently use machine vision methods, which are divided into two main methods.

[0005] A method that uses a large-format CCD color camera to shoot the entire screen at once, and then analyzes the color uniformity of each part of the entire picture. This method is widely used in the field of mobile phones and small-size PAD equivalent screens, and has achieved good results and benefits. However, this method of shooting the entire screen is not effective for large-size screens. This is mainly because the current screen emits polarized light, and the brightness is different when observed at different angles; to ensure that the screen light is incident on the camera at a close angle, a telephoto lens must be used, which makes the distance between the camera and the screen large enough.

[0006] One solution is to reduce the shooting field of view while using a telephoto lens, thereby significantly shortening the shooting distance from the screen; at the same time, the entire screen can be detected by moving the camera for multiple shots.

[0007] However, this method requires that the shooting state after each movement is consistent, that is, the distance and angle to the screen are consistent, the camera noise is consistent, and the ambient light interference is consistent. In reality, darkrooms are generally used to eliminate ambient light interference in production lines. The distance and angle to the screen are consistent by precisely placing the screen, the camera is perpendicular to the screen, and the camera movement is parallel to the screen plane. To achieve consistent noise, low-noise CCD cameras, large-size CCD chips, and optimized circuit processing chips are used.

[0008] Therefore, it is difficult to achieve the above-mentioned consistency. Summary of the invention

[0009] The embodiment of the present invention provides a method for detecting screen color uniformity, which overcomes the problem of "brightness differences of polarized light due to multiple observation angles" in large-size screen detection, and provides a reliable method for practical large-screen brightness uniformity detection.

[0010] According to an embodiment of the present invention, a method for detecting screen color uniformity is provided, comprising the following steps:

[0011] Acquire multiple pictures of the screen taken at multiple polarization angles, wherein the multiple pictures are obtained by taking multiple pictures of the screen with a backlight at a fixed position;

[0012] Based on multiple images obtained at multiple polarization angles, the grayscale value of the corresponding pixel is obtained for each image;

[0013] Based on the obtained multiple grayscale values, the phase difference of the polarization angle of each image is calculated;

[0014] Based on the phase difference, it is determined whether the polarized light of each image is linearly polarized light or circularly polarized light. According to whether it is linearly polarized light or circularly polarized light, it is calculated whether the corresponding pixel of the image is a point with uniform brightness.

[0015] Furthermore, based on the phase difference, it is determined whether the polarized light of each image is linearly polarized light or circularly polarized light. According to whether it is linearly polarized light or circularly polarized light, it is calculated whether the corresponding pixel of the image is uniform in brightness. Specifically, the following is the point:

[0016] When the phase difference is 0 or 180 degrees, the polarized light of the image is linearly polarized light. Based on the linearly polarized light, the corresponding pixel of the image is calculated to be a point where the brightness is uniform;

[0017] When the phase difference is not 0 degrees or 180 degrees, the polarized light of the image is circularly polarized light. Based on the circularly polarized light, it is calculated whether the corresponding pixel of the image is a point with uniform brightness.

[0018] Furthermore, when the phase difference is 0 degrees or 180 degrees, the polarized light of the image is linearly polarized light. Based on the linearly polarized light, the point at which the corresponding pixel of the image is calculated to determine whether the brightness is uniform is specifically:

[0019] When the phase difference is 0 degrees or 180 degrees, the polarized light is linearly polarized light, and the polarization azimuth of the linearly polarized light of each pixel is calculated;

[0020] Remove the maximum and minimum values ​​of the multiple polarization azimuths and calculate the average value of the remaining polarization azimuths;

[0021] When satisfied , the pixel is judged to be a point with uneven brightness, otherwise the pixel is judged to be a point with uniform brightness; wherein, is the average value of multiple polarization azimuths, θ represents any polarization azimuth, and σ1 is the set threshold.

[0022] Furthermore, when the phase difference is not 0 degrees or 180 degrees, the polarized light of the image is circularly polarized light, and the point of calculating whether the brightness of the corresponding pixel of the image is uniform is specifically:

[0023] When the phase difference is not 0 or 180 degrees, the polarized light is circularly polarized light, and the ellipse area corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated;

[0024] Based on the calculated major axis, minor axis and rotation angle of each ellipse, average values ​​of the major axis, minor axis and rotation angle are calculated respectively;

[0025] Construct a reference ellipse based on the average value of the major axis, minor axis and rotation angle, and calculate the area of ​​the reference ellipse;

[0026] When satisfied When , the pixel is judged to be a point with uneven brightness; where S is the difference between the area of ​​any ellipse and the area of ​​the reference ellipse, is the area of ​​the reference ellipse, and σ2 is the set threshold.

[0027] Furthermore, based on the multiple pictures corresponding to the multiple polarization angles, the grayscale value of the corresponding pixel in each picture is specifically:

[0028] Use a polarization camera that is perpendicular to the screen and fixed in position to obtain four pictures at four angles of the polarizer; the four angles are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

[0029] Furthermore, based on the obtained multiple grayscale values, the phase difference of the polarized light when acquiring the image is calculated as follows:

[0030] Take the grayscale values ​​of the corresponding pixels for the four pictures, the grayscale values ​​are I0, I 45 ,I 90 and I 135 ;

[0031] Based on the grayscale values ​​I0, I 45 ,I 90 and I 135 Calculate the parameters of polarized light, including intensity and phase difference.

[0032] Furthermore, based on the grayscale values ​​I0, I 45 ,I 90 and I 135 Calculate the parameters of polarized light, including the parameters A and B, and the phase difference δ;

[0033] The formula for calculating the phase difference is:

[0034]

[0035] Among them, A and B are the intensity of polarized light when the image is obtained at any two perpendicular angles, and δ is the phase difference of polarized light when the image is obtained at any two angles.

[0036] Furthermore, when the phase difference is 0 degrees or 180 degrees, the polarized light is linearly polarized light, and the polarization azimuth of the linearly polarized light of each pixel is calculated as follows:

[0037] First construct the Stocke variable as follows:

[0038]

[0039] Among them, S0, S1, and S2 are Stocks variables;

[0040] Then the polarization azimuth is calculated by the polarization angle formula;

[0041] The formula for polarization angle is:

[0042]

[0043] Or the polarization angle formula is:

[0044]

[0045] Where θ represents any polarization azimuth angle, is the average value of the polarization azimuth angle.

[0046] Furthermore, when the phase difference is not 0 degrees or 180 degrees, the polarized light is circularly polarized light, and the area of ​​the ellipse corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated as follows:

[0047] Based on the calculated parameters A and B, as well as the phase difference δ, the major axis, minor axis and rotation angle of the ellipse are calculated using the ellipse formula;

[0048] The formula for an ellipse is:

[0049]

[0050] Among them, a is the major axis of the ellipse, b is the minor axis of the ellipse, and φ is the rotation angle of the ellipse.

[0051] A screen color uniformity detection device, comprising:

[0052] Camera, the camera is used to capture images;

[0053] Polarizer: The polarizer is set on the camera, and the polarizer converts the light passing through the polarizer into polarized light of a set angle;

[0054] An angle adjuster, the angle adjuster is connected to the analyzer, and the movement of the angle adjuster drives the analyzer to rotate, thereby changing the polarization angle of the analyzer, so that the camera can capture images at different polarization angles;

[0055] The controller is connected to the camera to control the camera to take images at a fixed position and analyze and detect the images taken by the camera. The controller is also connected to the angle adjuster to control the angle adjuster to move.

[0056] Furthermore, the analyzer includes a polarizing film and a rotating gear, the polarizing film is arranged in the rotating gear, and the rotating gear is meshed with a motor gear on the angle adjuster.

[0057] Furthermore, the angle adjuster also includes a motor, the controller is connected to the motor and drives the motor to rotate, and the motor gear is arranged on the motor.

[0058] Furthermore, the detection device also includes an encoder, which is arranged on the motor to detect the rotation angle of the motor. The controller is connected to the encoder to obtain the angle detected by the encoder.

[0059] Furthermore, the detection device also includes a lens, which is located between the camera and the analyzer and is used to collect polarized light after passing through the analyzer.

[0060] Furthermore, the controller comprises:

[0061] A diffusion film detection module, which is connected to the camera and is used to detect the backlight after passing through the diffusion film and compare the uniformity of the backlight of images taken at different angles;

[0062] A polarizing film detection module, which is connected to the diffusion film detection module, is used to detect the backlight after passing through the diffusion film and the polarizing film, and compare the uniformity of polarized light of images taken at different angles;

[0063] The liquid crystal layer detection module is connected to the polarizing film detection module and is used to detect the backlight after passing through the diffusion film, the polarizing film and the liquid crystal layer, and to compare the uniformity of polarized light of images taken at different angles.

[0064] Furthermore, the controller further comprises:

[0065] The calculation module calculates whether the brightness uniformity of polarized light passing through the polarizing film and the liquid crystal layer is consistent.

[0066] Furthermore, a warning module is provided on the controller.

[0067] A computer-readable storage medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the steps in any of the above-mentioned screen color uniformity detection methods.

[0068] A terminal device comprises: a processor, a memory and a communication bus; the memory stores a computer-readable program executable by the processor;

[0069] The communication bus realizes the connection and communication between the processor and the memory;

[0070] When the processor executes the computer-readable program, the steps in any one of the above-mentioned screen color uniformity detection methods are implemented.

[0071] The screen color uniformity detection method and device in the embodiment of the present invention include: obtaining multiple pictures taken of the screen at multiple angles, wherein the multiple pictures are obtained by taking multiple pictures of the screen with backlight at a fixed position; based on the multiple pictures obtained at multiple polarization angles, taking the grayscale value of the corresponding pixel for each of the pictures; based on the multiple grayscale values ​​obtained, calculating the phase difference of the polarization angle of each of the pictures; based on the phase difference, judging whether the polarized light of each of the pictures is linear polarized light or circular polarized light; according to the linear polarized light or circular polarized light, calculating whether the corresponding pixel of the picture is a point with uniform brightness. The present application obtains pictures by fixed shooting, avoids the requirement of consistency of conditions due to the need to detect the screen by moving multiple shots, and overcomes the problem of "brightness difference of polarized light due to multiple observation angles" in screen detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0073] Figure 1 This is a flow chart of the screen color uniformity detection method of the present invention;

[0074] Figure 2 The schematic diagram of the screen color uniformity detection device of the present invention;

[0075] Figure 3 It is a schematic diagram of the screen backlight detection of the present invention;

[0076] Figure 4 A diagram of a reference ellipse of the present invention;

[0077] Figure 5 This is a schematic diagram of the terminal device of the present invention.

[0078] Reference numerals: 1 - camera, 2 - lens, 3 - analyzer, 301 - polarizing film, 302 - rotating gear, 4 - motor, 5 - motor gear, 6 - encoder, 7 - controller. DETAILED DESCRIPTION

[0079] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0080] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0081] See also Figure 1 According to an embodiment of the present invention, a method for detecting screen color uniformity is provided, comprising the following steps:

[0082] S101: Acquire multiple images of a screen taken at multiple polarization angles, wherein the multiple images are obtained by taking multiple images of a screen with a backlight at a fixed position;

[0083] S102: based on the multiple images correspondingly acquired at the multiple polarization angles, obtaining the gray value of the corresponding pixel for each image;

[0084] S103: Calculate and obtain the phase difference of the polarization angle of each image based on the obtained multiple grayscale values;

[0085] S104: Based on the phase difference, determine whether the polarized light of each image is linear polarized light or circular polarized light, and calculate whether the corresponding pixel of the image is a point with uniform brightness according to whether the linear polarized light or circular polarized light is a point with uniform brightness.

[0086] The screen color uniformity detection method and device in the embodiment of the present invention include: obtaining multiple pictures of the screen taken at multiple angles, wherein the multiple pictures are obtained by taking multiple pictures of the screen with backlight at a fixed position; taking the grayscale value of the corresponding pixel for each picture based on the multiple pictures obtained at multiple polarization angles; calculating the phase difference of the polarization angle of each picture based on the obtained multiple grayscale values; judging whether the polarized light of each picture is linearly polarized light or circularly polarized light based on the phase difference, and calculating whether the corresponding pixel of the picture is a point with uniform brightness according to the linear polarized light or circular polarized light. The present application obtains pictures by fixed shooting, avoids the requirement of consistency of conditions due to the need to detect the screen by moving multiple shots, and overcomes the problem of "brightness difference of polarized light due to multiple observation angles" in screen detection.

[0087] refer to Figure 1 and Figure 4 Based on the phase difference, determine whether the polarized light of each image is linearly polarized light or circularly polarized light. According to whether it is linearly polarized light or circularly polarized light, calculate whether the corresponding pixel of the image is uniform in brightness. Specifically:

[0088] When the phase difference is 0 or 180 degrees, the polarized light of the image is linearly polarized light. Based on the linearly polarized light, the corresponding pixel of the image is calculated to be a point where the brightness is uniform;

[0089] When the phase difference is not 0 degrees or 180 degrees, the polarized light of the image is circularly polarized light. Based on the circularly polarized light, it is calculated whether the corresponding pixel of the image is a point with uniform brightness.

[0090] The following are the specific steps for calculating whether the corresponding pixel of the image is a point with uniform brightness when the phase difference is 0 degrees or 180 degrees and the polarized light is linearly polarized light:

[0091] Step 1: When the phase difference is 0 degree or 180 degrees, the polarized light is linearly polarized light, and the polarization azimuth of the linear polarized light of each pixel is calculated;

[0092] Step 2: Remove the maximum and minimum values ​​of multiple polarization azimuth angles and calculate the average value of the remaining polarization azimuth angles;

[0093] Step 3: When satisfied When , the pixel is judged to be a point with uneven brightness; is the average value of multiple polarization azimuths, θ represents any polarization azimuth, and σ1 is the set threshold.

[0094] This application directly targets the principle of screen display polarization, and replaces the traditional screen uniformity detection method that relies on brightness based on the characteristics of polarized light. A polarizer is set in the camera. When the polarization camera is fixed and perpendicular to the screen, multiple pictures are taken at different polarizer angles. The phase difference of the polarized light when taking the picture is calculated by the phase difference formula. When the phase difference is 0 or 180 degrees, the polarized light is linearly polarized. After calculating the linear polarization azimuth of each picture pixel, the truncated mean is obtained. (i.e., calculating the mean after deleting some maximum and minimum values ​​in proportion), and setting the threshold σ; The pixels are judged as points with uneven brightness.

[0095] The following are the specific steps for calculating whether the corresponding pixel of the image is a point with uniform brightness when the phase difference is not 0 degrees or 180 degrees and the polarized light is circularly polarized light:

[0096] Step 1: When the phase difference is not 0 or 180 degrees, the polarized light is circularly polarized light, and the ellipse area corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated;

[0097] Step 2: Based on the calculated major axis, minor axis and rotation angle of each ellipse, respectively calculate the average values ​​of the major axis, minor axis and rotation angle;

[0098] Step 3: Construct a reference ellipse based on the average values ​​of the major axis, minor axis and rotation angle, and calculate the area of ​​the reference ellipse;

[0099] When satisfied When , the pixel is judged to be a point with uneven brightness; where S is the difference between the area of ​​any ellipse and the area of ​​the reference ellipse, is the area of ​​the reference ellipse, and σ2 is the set threshold.

[0100] If the phase difference calculated by the phase difference formula is not close to 0 or 180 degrees, the polarized light is circularly polarized. The three parameters of the major axis, minor axis and rotation angle of all ellipses need to be calculated by the ellipse formula. Then, the average of the calculated major axis, minor axis and rotation angle is calculated. The reference ellipse is constructed by averaging the major axis, minor axis and rotation angle. Its area is

[0101] Then calculate the difference between each ellipse and the reference ellipse, the area of ​​the difference is S; set the threshold, when , the pixel is determined to be an uneven point.

[0102] In the embodiment, based on the multiple pictures corresponding to the multiple polarization angles, the grayscale value of the corresponding pixel in each picture is specifically:

[0103] Use a polarization camera that is perpendicular to the screen and fixed in position to obtain four pictures at four angles of the polarizer; the four angles are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

[0104] In the embodiment, based on the obtained multiple grayscale values, the phase difference of the polarized light when acquiring the image is calculated as follows:

[0105] Take the grayscale values ​​of the corresponding pixels for the four pictures, which are I0, I 45 ,I 90 and I 135 ;

[0106] Based on the grayscale values ​​I0, I 45 ,I 90 and I 135 Calculate the parameters of polarized light, including intensity and phase difference.

[0107] The following is a detailed description of the screen color uniformity detection method of the present invention and the point of determining whether the pixel brightness is uneven by using a specific embodiment:

[0108] Step 1: With the polarization camera fixed and the screen vertical, take four pictures at different analyzer angles. The analyzer angles corresponding to these four pictures are 0 degrees, 45 degrees, 90 degrees, and 135 degrees, respectively.

[0109] Step 2: The four grayscale values ​​of the corresponding pixels are I0, I 45 ,I 90 and I 135 The four parameters A, B and two δ of polarized light are calculated from these four numbers through the phase difference formula, where A and B are the unit intensity of polarized light at two angles of the analyzer, and δ is the phase difference at the two angles.

[0110] The phase difference formula is:

[0111]

[0112] Among them, A and B are the intensity of polarized light when the image is obtained at any two perpendicular angles, and δ is the phase difference of polarized light when the image is obtained at any two angles.

[0113] Step 3: At this time, the calculated δ can be obtained in two cases. The first is when the calculated δ is 0 degree or 180 degree, or close to 0 degree or 180 degree; the second is when the phase difference is not 0 degree or 180 degree.

[0114] The first type: when the calculated δ is 0 degrees or 180 degrees, or close to 0 degrees or 180 degrees, that is, the phase difference is 0 or 180 degrees, the polarized light is linearly polarized light; the polarization azimuth of the linear polarized light of each pixel is calculated as follows:

[0115] First construct the Stocke variable as follows:

[0116]

[0117] The above S0, S1, S2 are Stocks variables

[0118] Then the polarization azimuth is calculated by the polarization angle formula;

[0119] The formula for polarization angle is:

[0120]

[0121] Alternatively, in order to reduce the error, the following polarization angle formula can also be used to calculate the linear polarization azimuth:

[0122]

[0123] Where θ represents any polarization azimuth angle, is the average value of the polarization azimuth, that is, the truncated mean is obtained after calculating the linear polarization azimuth of each pixel (i.e., calculating the mean after deleting some maximum and minimum values ​​in proportion), and setting the threshold σ; The pixels are judged as points with uneven brightness.

[0124] The second type: When δ is not close to 0 degrees or 180 degrees, the polarized light is circularly polarized light. The area of ​​the ellipse corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated. The specific steps of the relevant calculation are as follows:

[0125] Step 1: Based on the parameters A and B obtained by the above calculation, and the phase difference δ, the major axis, minor axis and rotation angle of the ellipse are calculated by the ellipse calculation formula;

[0126] The formula for an ellipse is as follows:

[0127]

[0128] Among them, a is the major axis of the ellipse, b is the minor axis of the ellipse, and φ is the rotation angle of the ellipse.

[0129] Step 2: After obtaining the major axis, minor axis, and rotation angle of each pixel, the truncated mean of the major axis, minor axis, and rotation angle of the ellipse are calculated respectively, and a reference ellipse is constructed based on the truncated mean of the major axis, minor axis, and rotation angle of the ellipse; where a is the major axis of the ellipse, b is the minor axis of the ellipse, φ is the rotation angle of the ellipse, and the area of ​​the reference ellipse is The figure of its reference ellipse is as follows Figure 4 shown.

[0130] Step 3: Calculate the ellipse figure composed of the major axis, minor axis and rotation angle of the ellipse corresponding to each pixel; calculate the area difference set between each ellipse figure and the reference ellipse figure, the area of ​​the difference set is S; set the threshold σ, when , then the pixel can be determined as an uneven point.

[0131] Furthermore, the similarity identification algorithm of the elliptically polarized light mentioned above may also include other types of algorithms, such as using phase difference or ellipse rotation angle as a similarity calculation reference; first calculating the truncated mean, and then comparing the difference with the threshold.

[0132] Furthermore, the scores of all pixels are set according to the above two calculation formulas (the above two similarity calculation methods of linear polarization and circular polarization), and image processing technology is used to realize block uneven point recognition and noise removal and other operations.

[0133] refer to Figure 3 The present invention uses a polarization camera to capture screen brightness at multiple polarization angles, and then calculates the incident light polarization angle of each pixel in the captured image based on the brightness information, thereby evaluating its brightness uniformity.

[0134] The method of this application requires that the brightness of the backlight source (after adding the diffusion film) is uniform and consistent, and the polarization angle of the backlight source after adding the polarization film is consistent. Therefore, in order to improve the quality of television products and more accurately detect the problems of television products, the method of the present invention is used to perform three-level detection on television products.

[0135] The following is a detailed description of the screen color uniformity detection method of the present invention for detecting television products using a specific embodiment:

[0136] First level inspection: add diffusion film for backlight inspection. After adding diffusion film, the backlight should be isotropic, non-polarized light with uniform brightness, and there is no pixel resolution requirement. Therefore, a CCD camera is used to shoot the entire screen vertically to detect whether the corresponding backlight meets the requirements; in order to increase the detection granularity, the camera position can be slightly shifted on the screen plane for multiple times to shoot, and the uniformity of each photo can be compared to increase the detection granularity; those that meet the requirements are released to the next process as qualified products.

[0137] Second-level detection: add polarizing film for backlight detection. The brightness of qualified (with diffusion film) backlight is consistent. As long as the polarization direction of the polarizing film is consistent, the brightness of the outgoing light is also consistent. Therefore, the polarization direction detection method of the present invention can be used to detect whether the polarization direction is consistent. If the polarization direction is consistent, it can be transferred to the next process for the third-level detection.

[0138] The third level detection: mainly for screen uniformity detection; in the above two tests, the backlight sources with consistent polarization direction and brightness are screened out; therefore, the screen brightness is completely determined by the polarization angle, and the detection of the screen brightness uniformity can be achieved by detecting the polarization angle in the third level detection.

[0139] This three-level detection solution can achieve accurate detection and control of each link of the backlight processing, and ultimately detect the screen brightness. At the same time, based on the calculation of the polarization direction of the light emitted by the screen, it can be used as a benchmark to adjust the brightness of multiple pictures taken in multiple areas, thus laying the foundation for the next detection of the screen based on multiple shots and the fusion of multiple pictures.

[0140] In the embodiment, if the screen backlight does not meet any level of detection, the screen is judged to be uneven in brightness. This application implements a complete closed-loop detection from backlight source to screen uniformity by detecting the screen three times, which can provide a data basis for production management and process improvement.

[0141] refer to Figure 2 and Figure 3 According to an embodiment of the present invention, a screen color uniformity detection device is provided, comprising:

[0142] Camera 1: Camera 1 is used to capture images;

[0143] Analyzer 3, which is disposed on the camera 1 and converts the light passing through the analyzer 3 into polarized light of a set angle;

[0144] An angle adjuster, which is connected to the analyzer 3. The movement of the angle adjuster drives the analyzer 3 to rotate, thereby changing the polarization angle of the analyzer 3, so that the camera 1 can capture images at different polarization angles.

[0145] The controller 7 is connected to the camera 1 to control the camera to take images at a fixed position and to analyze and detect the images taken by the camera 1. The controller 7 is also connected to the angle adjuster to control the movement of the angle adjuster.

[0146] The screen color uniformity detection device in the embodiment of the present application includes: a camera 1, which is used to capture images; an analyzer 3, which is arranged on the camera 1, and the analyzer 3 converts the light passing through the analyzer 3 into polarized light of a set angle; an angle adjuster, which is connected to the analyzer 3, and through the movement of the angle adjuster, drives the analyzer 3 to rotate, changes the polarization angle of the analyzer 3, so that the camera 1 can capture images at different polarization angles; a controller 7, which is connected to the camera 1, controls the capture of images, and analyzes and detects the images captured by the camera 1, and the controller 7 is also connected to the angle adjuster to control the movement of the angle adjuster. The present application controls the camera 1 to capture images at a fixed position through the controller 7, and adjusts the angle of the analyzer 3 through the angle adjuster, so that the analyzer 3 is at different polarization angles, thereby enabling the camera 1 to capture images at different polarization angles at a fixed position, thereby avoiding the problem of inconsistent environmental conditions for capturing images caused by the need to move the camera 1 to capture images at different angles.

[0147] Specifically, the controller 7 starts the motor 4 and detects the angle information detected by the encoder 6. After the polarizing film 301 reaches the set angle, the controller 7 controls the motor 4 to stop rotating, so that the polarizing film 301 is at the specified angle; the controller 7 controls the camera 1 to capture the image, and obtains the polarization image of the specified angle of the polarizing film 301; the motor 4 is repeatedly driven to drive the polarizing film 301 to reach a new set angle, and then the camera 1 is used to capture the image, so as to obtain polarization images of multiple polarization angles.

[0148] In the embodiment, the analyzer 3 includes a polarizing film 301 and a rotating gear 302. The polarizing film 301 is disposed inside the rotating gear 302. The rotating gear 302 is meshed with the motor gear 5 on the angle adjuster. The controller 7 controls the movement of the angle adjuster to drive the analyzer 3 meshed with the angle adjuster to rotate. The analyzer 3 rotates so that the camera 1 can capture images with different polarization angles at a fixed position.

[0149] In the embodiment, the angle adjuster further includes a motor 4, a controller 7 is connected to the motor 4 and drives the motor 4 to rotate, and a motor gear 5 is disposed on the motor 4. The controller 7 controls the motor 4 to rotate, and the motor 4 is provided with a motor gear 5, which meshes with the rotating gear 302, so that the controller 7 can drive the analyzer 3 to rotate by controlling the rotation of the motor 4.

[0150] In the embodiment, the detection device further includes an encoder 6, which is arranged on the motor 4 to detect the rotation angle of the motor 4, and the controller 7 is connected to the encoder 6 to obtain the angle detected by the encoder 6. The encoder 6 is arranged on the motor 4, and when the motor 4 rotates, the encoder 6 is used to detect the rotation angle of the motor 4, so that the rotation angle of the polarizing film 301 can be obtained, and the controller 7 obtains the rotation angle information detected by the encoder 6 by reading the encoder 6, and the controller 7 drives the motor 4 to rotate or stop rotating according to the obtained angle information.

[0151] In the embodiment, the detection device further includes a lens 2, which is located between the camera 1 and the analyzer 3 and is used to collect polarized light after passing through the analyzer 3. After passing through the analyzer 3, the light is converted into polarized light, and the lens 2 collects the polarized light, and the camera 1 captures the image through the lens 2.

[0152] In the embodiment, the controller 7 comprises:

[0153] A diffusion film detection module, which is connected to the camera and is used to detect the backlight after passing through the diffusion film and compare the uniformity of the backlight of images taken at different angles;

[0154] A polarizing film detection module is connected to the camera and is used to detect the backlight after passing through the diffusion film and the polarizing film, and compare the uniformity of polarized light of images taken at different angles;

[0155] The liquid crystal layer detection module is connected to the camera and is used to detect the backlight after passing through the diffusion film, the polarization film and the liquid crystal layer, and to compare the uniformity of polarized light of images taken at different angles.

[0156] Specifically, a diffusion film is added to the backlight of the screen, and the diffusion film detection module detects the backlight passing through the diffusion film; when it is detected that the uniformity of the image backlight is qualified, the polarizing film 301 is detected; when the polarizing film detection module detects that the backlight passing through the polarizing film 301 is qualified, the liquid crystal layer is detected; the polarizing film detection module detects the backlight after passing through the liquid crystal layer.

[0157] Specifically, the present application utilizes the polarization camera 1 to capture screen brightness at multiple polarization angles, and then calculates the incident light polarization angle of each pixel in the captured image based on the brightness information, thereby evaluating its brightness uniformity.

[0158] In the embodiment, a warning module is provided on the controller 7. The warning module is used to issue a warning that the screen has uneven brightness if the screen backlight does not meet the second preset condition or the third preset condition.

[0159] The purpose of the three tests is to detect the uniformity of the brightness of the screen. If the third preset condition is not met, the screen brightness is uneven. The pixel can be determined as a point with uneven brightness through the above method, and the controller 7 will issue a warning of uneven screen brightness.

[0160] In the embodiment, the controller 7 further includes:

[0161] The calculation module calculates whether the brightness uniformity of the polarized light passing through the polarizing film 301 and the liquid crystal layer is consistent.

[0162] The present application determines whether the uniformity of polarized light is consistent through calculation. The calculation method is the same as that in the above method embodiment, when the phase difference is 0 degrees or 180 degrees, and when the phase difference is not 0 degrees or 180 degrees, it is determined whether the pixel is an uneven point; the specific calculation process has been described in detail above and will not be repeated here.

[0163] Currently, some screen inspections are performed using machine vision methods, which are divided into two main methods:

[0164] The first method is to use a colorimetric camera to detect the color uniformity of several positions on the screen. This method can detect color and brightness information quite accurately. However, it has strict requirements on the measurement conditions. It requires that the angle of each measurement be perpendicular to the screen, and the distance from the probe to the screen should be fixed and short (to reduce peripheral brightness interference). Therefore, the detection speed is slow, and the detection range is quite small each time. It is generally used for production process control detection in random inspections.

[0165] The second method uses a large-format CCD color camera to capture the entire screen at once, and then analyzes the color uniformity of each part of the entire picture. This method is widely used in the field of mobile phones and small-size PAD equivalent size screens, and has achieved good results and benefits.

[0166] However, this method of shooting the entire screen is not very effective for large-size screens. This is mainly due to two factors:

[0167] The first factor is that the number of pixels in the CCD chip is generally required to exceed the number of pixels on the screen, so that pixel-level detection of the screen can be achieved; and the number of pixels on a large screen must be higher, for example, a 4K display screen has more than 4 million pixels;

[0168] The second factor is that the current screen emits polarized light, and the brightness is different when observed at different angles. To ensure that the angle of the screen light incident on the camera is close, a telephoto lens must be used, which requires the camera to be far enough away from the screen.

[0169] One solution is to reduce the shooting field of view while using a telephoto lens, thereby greatly shortening the shooting distance from the screen; at the same time, the entire screen can be detected by moving the camera multiple times. However, this method requires that the shooting state after each move is consistent, that is, the distance and angle to the screen are consistent, the camera noise is consistent, and the ambient light interference is consistent. In the actual production line, a darkroom is generally used to eliminate ambient light interference. The distance and angle to the screen are consistent by combining the precise placement of the screen, the camera being perpendicular to the screen, and the camera movement being parallel to the screen plane. In order to achieve consistent noise, a low-noise CCD camera, a large-size CCD chip, and an optimized circuit processing chip are used. However, it is difficult to achieve the consistency required by the above requirements.

[0170] Another idea is that the screen areas taken by the camera each time are overlapping, and the benchmark brightness between each picture can be adjusted by using the characteristic that the brightness of the overlapping area does not change for a short period of time. This requires considering the benchmark interference elimination mechanism when there is uneven brightness in the overlapping area, and solving the consistent comparison algorithm for the unified benchmark between multiple pictures. These problems make the related benchmark calculation method quite complicated.

[0171] The method of this application requires that the brightness of the backlight source (after adding the diffusion film) is uniform and consistent, and the polarization angle of the backlight source after adding the polarization film is consistent. Therefore, the present invention adopts a three-level detection mode.

[0172] refer to Figure 3 The screen color uniformity detection device of the present invention is described in detail with a specific embodiment as follows:

[0173] First level inspection: add diffusion film for backlight inspection. After adding diffusion film, the backlight should be isotropic, non-polarized light with uniform brightness, and there is no pixel resolution requirement. Therefore, CCD camera 1 is used to shoot the entire screen vertically to detect whether the corresponding backlight meets the requirements; in order to increase the detection granularity, the camera 1 position can be slightly shifted on the screen plane for multiple times and then taken. By comparing the uniformity of each photo, the detection granularity can be increased; those that meet the requirements are released to the next process as qualified products.

[0174] Second-level detection: add polarizing film for backlight detection. The brightness of qualified (with diffusion film) backlight is consistent. As long as the polarization direction of the polarizing film is consistent, the brightness of the outgoing light is also consistent. Therefore, the polarization direction detection method of the present invention can be used to detect whether the polarization direction is consistent. If the polarization direction is consistent, it can be transferred to the next process for the third-level detection.

[0175] The third level detection: mainly for screen uniformity detection; in the above two tests, the backlight sources with consistent polarization direction and brightness are screened out; therefore, the screen brightness is completely determined by the polarization angle, and the detection of the screen brightness uniformity can be achieved by detecting the polarization angle in the third level detection.

[0176] This three-level detection solution can achieve accurate detection and control of each link of the backlight processing, and ultimately detect the screen brightness. At the same time, based on the calculation of the polarization direction of the light emitted by the screen, it can be used as a benchmark to adjust the brightness of multiple pictures taken in multiple areas, thus laying the foundation for the next detection of the screen based on multiple shots and the fusion of multiple pictures.

[0177] Based on the above-mentioned screen color uniformity detection method, this embodiment provides a computer-readable storage medium, which stores one or more programs. The one or more programs can be executed by one or more processors to implement the steps in the screen color uniformity detection method as in the above-mentioned embodiment.

[0178] Based on the above screen color uniformity detection method, the present application also provides a terminal device, such as Figure 5 As shown, it includes at least one processor (processor) 20; display screen 21; and memory (memory) 22, and may also include a communications interface (CommunicationsInterface) 23 and a bus 24. Among them, the processor 20, the display screen 21, the memory 22 and the communication interface 23 can communicate with each other through the bus 24. The display screen 21 is set to display the user guide interface preset in the initial setting mode. The communication interface 23 can transmit information. The processor 20 can call the logic instructions in the memory 22 to execute the screen color uniformity detection method in the above embodiment.

[0179] In addition, the logic instructions in the memory 22 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product.

[0180] The memory 22 is a computer-readable storage medium that can be configured to store software programs, computer executable programs, such as program instructions or modules corresponding to the methods in the embodiments of the present disclosure. The processor 20 executes functional applications and data processing by running the software programs, instructions or modules stored in the memory 22, that is, implementing the methods in the above embodiments.

[0181] The memory 22 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required for at least one function; the data storage area may store data created according to the use of the terminal device, etc.

[0182] In addition, the memory 22 may include a high-speed random access memory and may also include a non-volatile memory, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program codes, or may be a transient storage medium.

[0183] The beneficial effects of the present invention are:

[0184] 1. This application implements a complete closed-loop detection from backlight source to screen uniformity by testing the screen three times, which can provide a data basis for production management and process improvement; by acquiring images through fixed shooting, it avoids the need for consistency of conditions due to the need to detect the screen by moving multiple shots, overcomes the problem of "brightness differences caused by multiple observation angles of polarized light" in screen detection, and provides support for feasible large-screen brightness uniformity. Compared with traditional methods, this solution can realize automatic detection, reduce manual burden, and improve product quality and consistency.

[0185] 2. The present application obtains screen images at a fixed position and performs automatic detection on the screen, thus avoiding the problem of human eye detection wasting human vision and the problem of insufficient detection accuracy and stability.

[0186] 3. This application completes three-level detection based on the present invention, realizing a complete closed-loop detection from backlight source to screen uniformity, which can provide a data basis for production management and process improvement.

[0187] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A screen color uniformity detection method, characterized in that: The following steps are involved: Acquire multiple pictures of the screen taken at multiple polarization angles, wherein the multiple pictures are obtained by taking multiple pictures of the screen with a backlight at a fixed position; Based on the multiple pictures correspondingly obtained at the multiple polarization angles, the grayscale value of the corresponding pixel in each of the pictures is obtained; Based on the obtained multiple grayscale values, calculate and obtain the phase difference of the polarization angle of each of the pictures; Based on the phase difference, determining whether the polarized light of each of the images is linearly polarized light or circularly polarized light, and calculating whether the corresponding pixel of the image is a point with uniform brightness according to the linearly polarized light or circularly polarized light; The method of judging whether the polarized light of each image is linear polarized light or circular polarized light based on the phase difference, and calculating whether the brightness of the corresponding pixel of the image is uniform according to the linear polarized light or circular polarized light is specifically as follows: When the phase difference is 0 degrees or 180 degrees, the polarized light of the image is linearly polarized light, and according to the linearly polarized light, it is calculated whether the corresponding pixel of the image is a point with uniform brightness; When the phase difference is not 0 degrees or 180 degrees, the polarized light of the image is circularly polarized light, and based on the circularly polarized light, it is calculated whether the corresponding pixel of the image is a point with uniform brightness.

2. The screen color uniformity detection method according to claim 1, characterized in that: When the phase difference is 0 degrees or 180 degrees, the polarized light of the image is linearly polarized light, and the point of calculating whether the brightness of the corresponding pixel of the image is uniform according to the linearly polarized light is specifically: When the phase difference is 0 degrees or 180 degrees, the polarized light is linearly polarized light, and the polarization azimuth of the linearly polarized light of each pixel is calculated; Remove the maximum and minimum values ​​of the plurality of polarization azimuths, and calculate the average value of the remaining polarization azimuths; When θ-θ≥σ1 is satisfied, the pixel is judged to be a point with uneven brightness, otherwise the pixel is judged to be a point with uniform brightness; wherein, is the average value of the plurality of polarization azimuth angles, θ represents any one of the polarization azimuth angles, and σ1 is the set threshold.

3. The screen color uniformity detection method according to claim 2, characterized in that: When the phase difference is not 0 degrees or 180 degrees, the polarized light of the image is circularly polarized light, and the point of calculating whether the brightness of the corresponding pixel of the image is uniform according to the circularly polarized light is specifically: When the phase difference is not 0 degree or 180 degrees, the polarized light is circularly polarized light, and the ellipse area corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated; Based on the calculated major axis, minor axis and rotation angle of each of the ellipses, respectively calculate the average values ​​of the major axis, minor axis and rotation angle; Constructing a reference ellipse based on the average values ​​of the major axis, the minor axis and the rotation angle, and calculating the area of ​​the reference ellipse; When satisfied When , the pixel is judged to be a point with uneven brightness; wherein S is the difference between the area of ​​any one of the ellipses and the area of ​​the reference ellipse, is the area of ​​the reference ellipse, and σ2 is the set threshold.

4. The screen color uniformity detection method according to claim 3, characterized in that: Based on the multiple pictures correspondingly obtained at multiple polarization angles, the grayscale value of the corresponding pixel in each picture is specifically: Use a polarization camera that is perpendicular to the screen and fixed in position to obtain four pictures at four angles of the polarizer; the four angles are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively.

5. The screen color uniformity detection method according to claim 4, characterized in that: The phase difference of polarized light when acquiring the image is calculated based on the acquired multiple grayscale values ​​is specifically: Take the grayscale values ​​of the corresponding pixels for the four pictures, and the grayscale values ​​are I0, I 45 ,I 90 and I 135 ; Based on the grayscale values ​​I0, I 45 ,I 90 and I 135 Calculate the parameters of polarized light, including light intensity and phase difference.

6. The screen color uniformity detection method according to claim 5, characterized in that: The grayscale values ​​I0, I 45 ,I 90 and I 135 Calculate the parameters of polarized light, including the parameters A and B, and the phase difference δ; The formula for calculating the phase difference is: Among them, A and B are the intensity of polarized light when the image is obtained at any two perpendicular angles, and δ is the phase difference of polarized light when the image is obtained at any two angles.

7. The screen color uniformity detection method according to claim 6, characterized in that: When the phase difference is 0 degrees or 180 degrees, the polarized light is linearly polarized light, and the polarization azimuth of the linearly polarized light of each pixel is calculated as follows: First construct the Stocke variable as follows: Wherein, S0, S1, S2 are Stocks variables; Then the polarization azimuth is calculated by the polarization angle formula; The polarization angle formula is: Or the polarization angle formula is: Wherein, the θ represents any one of the polarization azimuth angles, is the average value of the polarization azimuth angles.

8. The screen color uniformity detection method according to claim 6, characterized in that: When the phase difference is not 0 degrees or 180 degrees, the polarized light is circularly polarized light, and the area of ​​the ellipse corresponding to each pixel and the major axis, minor axis and rotation angle of each ellipse are calculated as follows: Based on the calculated parameters A and B, and the phase difference δ, the major axis, the minor axis and the rotation angle of the ellipse are calculated by using an ellipse formula; The ellipse formula is: Among them, a is the major axis of the ellipse, b is the minor axis of the ellipse, and φ is the rotation angle of the ellipse.

9. A screen color uniformity detection device, characterized in that: Applied to the screen color uniformity detection method according to any one of claims 1 to 8, the device comprises: A camera, wherein the camera is used to capture images; An analyzer, the analyzer is arranged on the camera, and the analyzer converts the light passing through the analyzer into polarized light of a set angle; An angle adjuster, the angle adjuster is connected to the analyzer, and the analyzer is driven to rotate by the movement of the angle adjuster, thereby changing the polarization angle of the analyzer, so that the camera can capture images at different polarization angles; A controller, the controller is connected to the camera, controls the camera to capture images at a fixed position, and analyzes and detects the images captured by the camera. The controller is also connected to the angle adjuster, and controls the angle adjuster to move; The controller comprises: A diffusion film detection module, which is connected to the camera and is used to detect the backlight after passing through the diffusion film and compare the uniformity of the backlight of the images taken at different angles; A polarizing film detection module, which is connected to the camera and is used to detect the backlight after passing through the diffusion film and the polarizing film, and compare the uniformity of the polarized light of the image taken at different angles; A liquid crystal layer detection module is connected to the camera and is used to detect the backlight after passing through the diffusion film, the polarization film and the liquid crystal layer, and to compare the uniformity of the polarized light of the images taken at different angles.

10. The screen color uniformity detection device according to claim 9, characterized in that: The polarizer comprises a polarizing film and a rotating gear, wherein the polarizing film is arranged inside the rotating gear, and the rotating gear is meshed with a motor gear on the angle adjuster.

11. The screen color uniformity detection device according to claim 9, characterized in that: The angle adjuster also includes a motor, the controller is connected to the motor and drives the motor to rotate, and the motor gear is arranged on the motor.

12. The screen color uniformity detection device according to claim 11, characterized in that: The detection device further comprises an encoder, which is arranged on the motor and detects the rotation angle of the motor. The controller is connected to the encoder to obtain the angle detected by the encoder.

13. The screen color uniformity detection device according to claim 9, characterized in that: The detection device also includes a lens, which is located between the camera and the analyzer and is used to collect polarized light after passing through the analyzer.

14. The screen color uniformity detection device according to claim 9, characterized in that: The controller further comprises: A calculation module is used to calculate whether the brightness uniformity of polarized light passing through the polarizing film and the liquid crystal layer is consistent.

Images