A display screen chroma stability quantification method and evaluation method

Abstract

The present application relates to a kind of display screen chroma stability quantification method and evaluation method, based on the chroma change generated by display screen over time, it is proposed to be quantified by chroma attenuation speed v to express the display stability performance of display screen, for the analysis and evaluation of display screen chroma stability performance.It includes: obtaining first image, lighting target display screen obtains the first image of pure color chroma;Extract first calculation area, select first calculation area in first image, and obtain the CI E value (X1, Y1, L1) of all points in first calculation area.Get second image, after t minutes, obtain the CI E value (X2, Y2, L2) of all points corresponding to first calculation area in second image;Calculate the color decay rate V in first calculation area, respectively calculate the X value decay rate Vx and Y value decay rate Vy corresponding to each pixel point, color decay rate V=(Vx+Vy) / 2, color decay rate V is as one of display screen chroma stability quantification index, the smaller the color decay rate value is, then be considered as the display of this display screen is more stable.

Description

Technical Field

[0001] This invention relates to the field of display screen performance measurement technology, and specifically to a method for quantifying and evaluating the color stability of a display screen. Background Technology

[0002] With the rapid development of the information technology industry, flat panel displays are playing an increasingly important role in people's daily lives. High-end displays often feature thinness, wide color gamut, high resolution, high contrast, short response time, and flexibility.

[0003] Before a display is designed or shipped, it undergoes extensive optical performance testing to ensure it meets the requirements of a high-quality display. Among these tests, color uniformity is typically assessed. Examples include: maximum brightness non-uniformity, low brightness non-uniformity, black screen non-uniformity, and color uniformity.

[0004] However, while most monitors possess color stability, color accuracy gradually decreases over time. For example, when testing a white screen, the white display may slowly turn bluish over time. This bluish tint is subtle and imperceptible to the naked eye for designers or testers, and there are no specific metrics in the display testing industry to represent this color change.

[0005] Furthermore, the applicant discovered through testing that over time, some white screens gradually shift towards a slight yellow tint, while others shift towards a bluish tint. The difference in color decay rate is even more pronounced when switching to a solid color interface.

[0006] In the optical performance testing process in this field, the evaluation of color stability in displays has been neglected. As users now have increasingly higher performance requirements for displays, there is an urgent need for a quantitative method to assess color stability, enabling designers and testing personnel to easily determine whether a display possesses high-standard performance through this quantitative indicator, thereby further ensuring the high-quality requirements of the display. Summary of the Invention

[0007] This invention proposes a method for quantifying and evaluating the color stability of a display screen. Based on the color change of the display screen over time, it proposes to quantify the display stability performance of the display screen by using the color decay rate v, which is used for the analysis and evaluation of the color stability performance of the display screen.

[0008] Specifically, a method for quantifying the color stability of a display screen is proposed, which includes:

[0009] Acquire the first image and illuminate the target display screen by acquiring the first image of the pure color chromaticity through the acquisition device;

[0010] Extract the first calculation region, select an effective region within the first image as the first calculation region, and obtain the CIE values ​​(X1, Y1, L1) of all points within the first calculation region, where X1 and Y1 are the chromaticity of the corresponding pixel, and L1 represents the brightness of the corresponding pixel.

[0011] Acquire the second image, and after t minutes, acquire the CIE values ​​(X2, Y2, L2) of all points in the second image corresponding to the first calculation region;

[0012] Calculate the color decay rate V in the first calculation area, and calculate the X value decay rate Vx and Y value decay rate Vy corresponding to each pixel. Color decay rate V = (Vx + Vy) / 2. Use color decay rate V as one of the quantitative indicators of color stability of the display screen. The smaller the color decay rate value, the more stable the display screen is considered.

[0013] As a preferred technical solution, the above-mentioned X-value decay rate Vx is calculated as Vx=(|X2-X1| / X1) / t; Y-value decay rate Vy=(|Y2-Y1| / Y1) / t.

[0014] As a preferred technical solution, the first calculation area is the center pixel or a center pixel area extending outward at equal distances from the center pixel.

[0015] As a preferred technical solution, when the first calculation area is a central pixel area extending outward at equal distances from the central pixel, the average color decay rate value of the central pixel area and the average absolute error value of each edge pixel are calculated based on the color decay rate value. If the average absolute error values ​​of the edge pixels are close, the smaller the average color decay rate value, the more stable the display screen is considered to be.

[0016] As a preferred technical solution, the aforementioned pure color hues include pure white, pure red, pure green, and pure blue.

[0017] As a preferred technical solution, the target display screen is color-calibrated before being turned on.

[0018] The present invention also provides a method for evaluating the color stability of a display screen. The stability quantification method described above is used to evaluate the color stability of the display screen. The smaller the value of the color decay rate V, the more stable the display screen is considered to be.

[0019] As a preferred technical solution, the above evaluation method further includes: when the first calculation area is the center pixel, the brightness decay rate VL = (|L2-L1| / L1) / t of the center pixel is also calculated; when the brightness decay rate VL ≈ color decay rate V, the display screen is evaluated as stable.

[0020] As a preferred technical solution, the above-mentioned display screen color stability evaluation method further includes: when the first calculation area is a central pixel area extending outward at equal distances from the central pixel, calculating the weighted average color decay rate of the central pixel area. Weighted average color decay rate The smaller the value, the more stable the display is considered to be.

[0021] As a preferred technical solution, when the first calculation region is a central pixel region extending outward at equal distances from the central pixel, the weighted average color decay rate is... The weights from the center outwards are 1, 0.95, 0.9, 0.85, and so on.

[0022] Compared with the prior art, the present invention achieves the following technical effects: The present invention obtains the CIE value of a portion of the effective area in the solid color display image, and after a period of time, obtains the CIE value of that portion again, calculates the chromaticity decay rate of that area, and can intuitively compare the display stability of the two screens through the quantitative index of chromaticity decay rate, thereby facilitating further evaluation and analysis of the display effect.

[0023] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. Attached image description:

[0024] Figure 1 A schematic diagram of the display screen color stability quantification method proposed in Embodiment 1 of the present invention;

[0025] Figure 2 A schematic diagram of the connection of the display screen color stability quantization device proposed in Embodiment 1 of the present invention;

[0026] Figure 3 A schematic diagram of the fixing device structure proposed in Embodiment 2 of the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] First image acquisition unit 101; First calculation region CIE value extraction unit 102; Second image acquisition unit 103; Color decay rate V calculation unit 104;

[0029] Graphite fixing tank 110; tank bottom plate 111; air inlet 112; turbulent fluid 113; dehumidifier 114; acrylic cover plate 120; hot air circulation assembly 130; micro circulating fan 131; electric heater 132. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0031] It should be understood that the steps described in the method embodiments of this application may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of this application is not limited in this respect.

[0032] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0033] It should be noted that the terms "one" and "multiple" used in this application are illustrative rather than restrictive, and those skilled in the art should understand that, unless explicitly stated otherwise in the context, they should be understood as "one or more". "Multiple" should be understood as two or more.

[0034] Example 1

[0035] In the early stages of display development or to ensure the quality of the display before it leaves the factory, color uniformity testing is usually conducted. If the color is not uniform, it is professionally calibrated to make the color deviation relatively smaller.

[0036] Although the lifespan of display screen light sources is long, color degradation can still occur after prolonged operation and / or at high temperatures. This can manifest as reduced brightness and subtle changes in actual color, affecting the overall color consistency of the display screen. There are many reasons that can lead to uneven color on a display screen, such as: inherent degradation of the LED light source itself; and different degradation rates among LEDs used by different manufacturers or in different production batches.

[0037] When a display screen actually produces minute color changes, users or inspectors may not be able to perceive these changes during the verification process. Therefore, a quantitative method is needed to help R&D or inspection personnel easily see whether the color display effect of the display screen is stable. By using a quantitative value to characterize the color stability of the display screen, it can be used to distinguish different grades of LED lights and different stability performances, which facilitates further comparison and evaluation of the display screen's performance and lays the foundation for the later automated batch selection of different grades of display screens.

[0038] For details, please refer to [link / reference]. Figure 1 This embodiment provides a method for quantifying the color stability of a display screen, used to evaluate whether the display effect of the display screen will remain unchanged over time and under usage conditions, or whether it will be distorted. The quantification method includes:

[0039] S1: Acquire the first image and turn on the target display screen. Acquire the first image of pure color chromaticity through the acquisition device.

[0040] Specifically, to ensure the effectiveness of the evaluation of display color stability, the target display is color-calibrated before being turned on to ensure uniform color display. After color calibration, the display is turned off and allowed to cool to room temperature before being turned on to eliminate the temperature effect after color calibration.

[0041] After the target display screen is lit, a first image is acquired using a data acquisition device. This device can be a CCD camera or other lens-type optical sensor capable of rapid calibration and processing of shadow details and white balance. This ensures that the acquired first image is color-accurate.

[0042] In this embodiment, a CCD camera is selected. By setting the distance between the CCD camera and the display screen to be inspected, the color analyzer performs white balance correction, and the display screen to be inspected is fixed on the machine vision data acquisition platform. To avoid interference from other stray light, the acquisition environment is a dark room, and the first image is acquired.

[0043] In this step, the first image color obtained is a pure color, including pure white, pure red, pure green, and pure blue. In this embodiment, pure white, which is commonly used in display screen detection, is selected.

[0044] S2: Extract the first calculation region, select an effective region within the first image as the first calculation region, and obtain the CIE values ​​(X1, Y1, L1) of all points within the first calculation region, where X1 and Y1 are the chromaticity of the corresponding pixel, and L1 represents the brightness of the corresponding pixel.

[0045] In this step, a first calculation region is selected from the first image. This first calculation region can be any area within the first image or the entire screen. In this embodiment, to ensure detection speed, a representative center point is selected as the first calculation region, and then the CIE value (X1, Y1, L1) of the center point pixel is obtained.

[0046] S3: Obtain the second image. After t minutes, obtain the CIE values ​​(X2, Y2, L2) of all points in the second image corresponding to the first calculation region.

[0047] After acquiring the CIE value of the center point, wait t minutes and then acquire a second image using the same image acquisition device. Theoretically, the longer the time t is, the more accurate the measurement of the color stability of the display screen. In this embodiment, the value of t is selected as 5 minutes. That is, after 5 minutes, the CIE value (X2, Y2, L2) of the center point on the second image is obtained.

[0048] S4: Calculate the color decay rate V within the first calculation area. Calculate the X-value decay rate Vx and Y-value decay rate Vy for each pixel. Color decay rate V = (Vx + Vy) / 2. Use color decay rate V as one of the quantitative indicators of display color stability. The smaller the color decay rate value, the more stable the display is considered. Evaluate the display effect and the rate of display distortion over time.

[0049] Among them, the X-value decay rate Vx is calculated as Vx=(|X2-X1| / X1) / t; the Y-value decay rate Vy=(|Y2-Y1| / Y1) / t; and the color decay rate V=(Vx+Vy) / 2.

[0050] In this embodiment, two displays were selected and the above operations were performed. For different pairs of displays, the color decay rate was calculated by testing, which allows for a direct comparison of the display stability of the two displays. The test data obtained is shown in the table below:

[0051]

[0052] As can be seen from the table above, the color decay rate of the first display screen is less than that of the second display screen. It can be determined that, over time, the display effect of the first display screen changes less than that of the second display screen. Therefore, the display effect of the first display screen is better and more stable.

[0053] This embodiment also provides a method for evaluating the color stability of a display screen. The above-mentioned stability quantification method is used to evaluate the color stability of the display screen. The smaller the value of the color decay rate V, the more stable the display screen is considered to be.

[0054] This embodiment also provides a display screen color stability quantization device; please refer to [link / reference]. Figure 2 It includes:

[0055] The first image acquisition unit 101 illuminates the target display screen and acquires a first image of pure color chromaticity through the acquisition device;

[0056] The first calculation region CIE value extraction unit 102 selects an effective region within the first image as the first calculation region and obtains the CIE values ​​(X1, Y1, L1) of all points within the first calculation region, where X1 and Y1 are the chromaticity of the corresponding pixel and L1 represents the brightness of the corresponding pixel.

[0057] The second image acquisition unit 103 acquires the CIE values ​​(X2, Y2, L2) of all points corresponding to the first calculation region on the second image after t minutes.

[0058] The color decay rate V calculation unit 104 calculates the X value decay rate Vx and Y value decay rate Vy corresponding to each pixel point respectively. The color decay rate V = (Vx + Vy) / 2. The color decay rate V is used as one of the quantitative indicators of the color stability of the display screen. The smaller the color decay rate value, the more stable the display screen is considered to be.

[0059] Example 2

[0060] This embodiment optimizes upon embodiment 1. Since the acquisition time interval between the second and first images in embodiment 1 is 5 minutes, the display screen's illumination time is short, which may affect the accuracy of the chromaticity stability quantification result. Therefore, to further improve the accuracy of the display screen's chromaticity stability quantification result, this embodiment also designs a fixing device for securing the display screen under inspection on the machine vision data acquisition platform. Please refer to [link to relevant documentation]. Figure 3 .

[0061] The fixing device includes a graphite fixing groove 110, an acrylic cover plate 120, and a hot air circulation assembly 130 disposed within the graphite fixing groove 110. Specifically, a groove bottom plate 111 with an array of through holes is provided in the middle of the graphite fixing groove 110. The groove bottom plate 111 divides the graphite fixing groove 110 into an upper groove for fixing the display screen to be tested and a lower housing for assembling the hot air circulation assembly 130. A detachable or movable acrylic cover plate 120 is also provided on the top of the upper groove. In this embodiment, the acrylic cover plate 120 is fixed to the graphite fixing groove 110 by a pivot. When it is necessary to take pictures, the acrylic cover plate 120 can be flipped open.

[0062] An air inlet 112 is located at the bottom of one side of the lower housing. The hot air circulation assembly 130 includes a micro-circulating fan 131, an electric heater 132, and a hot air circulation controller that connects to and controls the micro-circulating fan 131 and the electric heater 132, maintaining the hot air temperature between 30℃ and 50℃. A turbulence flow 113, rectangular at the bottom and hemispherical at the top, is fixedly installed in the middle of the lower housing. The turbulence flow 113 divides the lower housing space into a circulating hot air duct with an arc-shaped channel at the top and a U-shaped channel at the bottom. The micro-circulating fan 131, the electric heater 132, and the hot air circulation controller are mounted in the lower horizontal channel of the U-shaped channel. An air inlet 112 is located on the side of the lower housing, and a dehumidifier 114 is installed at the air inlet 112. The dehumidifier 114 is replaceable.

[0063] After capturing the first image, the acrylic cover 120 is placed on top, and the micro circulating fan 131 and electric heater 132 are started, so that the display in the graphite fixing slot 110 is in a low-speed hot air environment. Thus, during the continuous lighting process, the display can simulate the display working in a high-temperature environment, shorten the stability measurement time of the display, and will not damage the display.

[0064] Under continuous hot air environment, after 5 minutes, the CIE value (X2, Y2, L2) of the center point on the second image is obtained.

[0065] This ensures that the captured second image will not damage the display screen and can better match the high-intensity operation of the display screen.

[0066] Example 3

[0067] This embodiment 3 is based on embodiment 1 or embodiment 2, and it optimizes the display screen color stability evaluation method. In addition to only determining the color decay rate V, the specific display screen color stability evaluation method also includes: when the first calculation area is the center pixel, it also calculates the brightness decay rate VL of the center pixel = (|L2-L1| / L1) / t; when the brightness decay rate VL ≈ color decay rate V, the display screen is evaluated as stable.

[0068] For example, in the first display screen of Embodiment 1, the color decay rate V is 0.04%, and the calculated brightness decay rate VL is also 0.04%. Therefore, the color evaluation of the first display screen is highly stable.

[0069] Example 4

[0070] This embodiment 4 is a preferred technical solution based on embodiment 1, embodiment 2, or embodiment 3. In this embodiment, the first calculation region, besides being the center pixel as in embodiment 1, is a region of central pixels extending outwards at equal distances from the center pixel. This equal-distance extension can be one or two pixels, which not only increases the accuracy of the quantization result for color stability but also has a very short calculation time, making it acceptable in terms of quantization speed.

[0071] As a preferred technical solution, when the first calculation area is a central pixel area extending outward at equal distances from the central pixel, the method for evaluating the color stability of the display screen is further optimized.

[0072] That is, the average color decay rate of the central pixel area and the average absolute error of each edge pixel can be calculated based on the color decay rate value. If the average absolute error of the edge pixels is close, the smaller the average color decay rate value, the more stable the display is considered to be.

[0073] The average color decay rate is calculated as follows: the sum of color decay rate values ​​for all center pixel regions divided by the number of pixels in the center pixel region. The average absolute error of each edge pixel is calculated as: the sum of the differences between the color decay rate value of each edge pixel and the average color decay rate value divided by the number of edge pixels.

[0074] In this embodiment, by introducing the average absolute error value of the color decay rate value of the edge points other than the center pixel point, the magnitude of the color decay rate value measured at the edge pixels and the actual prediction error can be accurately reflected.

[0075] Furthermore, based on the magnitude of the color decay rate value and the actual prediction error, the measured color decay rate of edge pixels is weighted to eliminate the influence of error on the accuracy of the quantization result of color stability.

[0076] As a preferred technical solution, the above-mentioned display screen color stability evaluation method further includes calculating the weighted average color decay rate of the central pixel region when the first calculation region is a central pixel region extending outward at equal distances from the central pixel. Weighted average color decay rate The smaller the value, the more stable the display is considered to be.

[0077] Specifically, when the first calculation region is a central pixel region extending equidistantly outward from the central pixel, the weighted average color decay rate... The weights from the center outwards are 1, 0.95, 0.9, 0.85, and so on.

[0078] This invention focuses on measuring the color decay rate of a display screen. By quantifying the color decay rate, it facilitates the evaluation and analysis of display screen performance. A smaller color decay rate (V) indicates less color change and display quality variation over time, resulting in a more stable display. The quantified color decay rate provides a clear description of this attribute, simplifying both initial project evaluation and subsequent comparative analysis. Based on this core concept, a new method for evaluating the color stability of display screens has been developed, facilitating performance rating of displays.

[0079] In summary, the present invention achieves the following technical effects compared to the prior art: The present invention obtains the CIE value of a portion of the effective area in a solid color display image, and after a period of time, obtains the CIE value of that portion again, calculates the chromaticity decay rate of that area, and uses this quantitative indicator of chromaticity decay rate to intuitively compare the display stability of two screens, thereby facilitating further evaluation and analysis of the display effect.

[0080] Those skilled in the art will recognize that the methods and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0081] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices or units, or may be electrical, mechanical or other forms of connection.

[0082] The units described as separate components may or may not be physically separate. As will be appreciated by those skilled in the art, the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0083] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0084] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or grid device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0085] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for evaluating chromaticity stability of a display screen, characterized by, This evaluation method uses a display screen color stability quantification method to evaluate the color stability of the display screen, the stability quantification method including: Acquire a first image by lighting up the target display screen and obtaining a first image of pure color chromaticity using an acquisition device; the acquisition of the first image is performed in a darkroom environment. Extract the first calculation region, select an effective region within the first image as the first calculation region, and obtain the CIE values ​​(X1, Y1, L1) of all points within the first calculation region, where X1 and Y1 are the chromaticity of the corresponding pixel, and L1 represents the brightness of the corresponding pixel. Acquire the second image, and after t minutes, acquire the CIE values ​​(X2, Y2, L2) of all points in the second image corresponding to the first calculation region; The color decay rate V within the first calculation region is calculated, and the X-value decay rate Vx and Y-value decay rate Vy corresponding to each pixel are calculated respectively. The color decay rate V = (Vx + Vy) / 2. The color decay rate V is used as one of the quantitative indicators of the color stability of the display screen. The smaller the color decay rate value, the more stable the display screen is considered to be. The first calculation region is the center pixel or a central pixel area extending outward at equal distances from the center pixel. When the first calculation region is a central pixel area extending outward at equal distances from the center pixel, the average color decay rate value of the central pixel area and the average absolute error value of each edge pixel are calculated based on the color decay rate value. If the average absolute error values ​​of the edge pixels are close, the smaller the average color decay rate value, the more stable the display screen is considered to be. The pure color chromaticity includes pure white, pure red, pure green, and pure blue. The smaller the value of the color decay rate V, the more stable the display screen is considered to be; The evaluation method also includes: when the first calculation area is the center pixel, the brightness decay rate VL = (|L2-L1| / L1) / t of the center pixel is also calculated; when the brightness decay rate VL ≈ color decay rate V, the display screen is evaluated as stable.

2. The method for evaluating the color stability of a display screen according to claim 1, characterized in that, The decay rate Vx of the X value is calculated as Vx = (|X2-X1| / X1) / t; the decay rate Vy of the Y value is calculated as Vy = (|Y2-Y1| / Y1) / t.

3. The method for evaluating the color stability of a display screen according to claim 1, characterized in that, Before illuminating the target display screen, the target display screen is color calibrated.

4. The method for evaluating the color stability of a display screen according to claim 1, characterized in that, The method for evaluating the color stability of the display screen further includes: when the first calculation area is a central pixel area extending outward at equal distances from the central pixel, calculating the weighted average color decay rate of the central pixel area; if the value of the weighted average color decay rate is smaller, the display screen is considered to be more stable.

5. The method for evaluating the color stability of a display screen according to claim 4, characterized in that, When the first calculation region is a central pixel region extending outward at equal distances from the central pixel, the weights of the weighted average color decay rate from the center outward are 1, 0.95, 0.9, 0.85, ...

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