A method for screening chrominance difference of LED display module

Abstract

The present application relates to a kind of LED display module chromaticity difference screening method, the method is as follows: for each LED display module of a batch, in darkroom environment with area array camera measurement obtains its CIE1931 color space three stimulus value and conversion to uniform color space, the chromaticity difference of each LED display module is calculated in uniform color space;The LED display module with chromaticity difference greater than or equal to the set chromaticity difference threshold in the batch is screened out.The present application can select the display module with chromaticity difference in a batch of LED display modules, and it is screened out, and then the remaining display module after luminance correction is spliced module, box or display screen, compared with chromaticity correction, save one third of time, and will not cause gamut loss, can effectively weaken the uneven phenomenon that chromaticity is distributed by block after display screen lighting.

Description

Technical Field

[0001] The invention belongs to the technical field of LED display optical acquisition and correction, and relates to a method for screening chromaticity differences of LED display modules. Background Art

[0002] LED displays are composed of countless red, green, and blue LED die. The wavelength and bandwidth of these LED die exhibit a certain degree of discreteness, and even under the same drive current, the brightness and chromaticity of these LED die also exhibit discreteness. Generally, display manufacturers require component suppliers to provide LEDs with a wavelength range of 5nm and a brightness range of 1:1.3. The wavelength-brightness binning method currently widely used in the industry has certain limitations, especially on high-density, fine-pitch displays. This is because even though the wavelength data of the light-emitting chips is within the same range, the saturation varies, causing the color coordinates to exceed the range of color difference that the human eye can discern.

[0003] Large LED screens are assembled and spliced ​​from display modules. The discreteness of the light-emitting chips can lead to uneven brightness or color of the display modules. Brightness or color correction can effectively improve uniformity, but in actual projects, since brightness correction does not change its color coordinates, performing color correction on each display module will waste a lot of time. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for screening chromaticity differences of LED display modules. Through this method, display modules with chromaticity differences can be selected and screened out, and then the remaining display modules that have undergone brightness correction can be used to splice modules, boxes or display screens, eliminating the chromaticity correction step and improving work efficiency.

[0005] In order to solve the above technical problems, the chromaticity difference screening method of the LED display module of the present invention is as follows:

[0006] For each LED display module in a batch, use an area scan camera to measure its CIE1931 color space tristimulus values ​​in a darkroom. When measuring the X, Y, and Z values, place an X filter, a Y filter, and a Z filter in front of the area scan camera lens, respectively. The final X, Y, and Z tristimulus values ​​in the CIE1931 color space are calculated using the following formula:

[0007]

[0008]

[0009]

[0010] Wherein, FinX(i), FinY(i), and FinZ(i) are the final X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space; CamX(i), CamY(i), and CamZ(i) are the actual X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space measured by the area array camera; i = 1, 2…, N, where N is the number of LED display modules in this batch. are the transformation matrices of the X, Y, and Z components respectively;

[0011] The final X, Y, and Z tristimulus values ​​of the CIE1931 color space of each LED display module are converted to a uniform color space, and the chromaticity difference of each LED display module is calculated in the uniform color space; LED display modules in the batch with a chromaticity difference greater than or equal to a set chromaticity difference threshold are filtered out.

[0012] Furthermore, a plurality of LED display modules used to splice a module, a box or a display screen constitutes a batch of LED display modules.

[0013] Furthermore, the LED display modules in one module and the LED display modules around it together constitute a batch of LED display modules.

[0014] Furthermore, for each LED display module, red, green, and blue can be displayed at its highest grayscale level and measured using an area array camera in a darkroom environment to obtain the measured tristimulus values ​​in the CIE1931 color space corresponding to the three primary colors of red, green, and blue.

[0015] Furthermore, for each LED display module, when only blue is displayed at its highest grayscale, it can be measured using an area array camera in a darkroom environment to obtain the measured tristimulus values ​​in the CIE1931 color space corresponding to the three blue primary colors.

[0016] Furthermore, for any LED display module, the final X, Y, and Z tristimulus values ​​of the CIE1931 color space are converted to the CIE-LAB uniform color space using the following formula to obtain the lightness L of the LED display module in the CIE-LAB uniform color space: * and chroma a * 、b * ;

[0017]

[0018]

[0019] Where FinX(i), FinY(i), and FinZ(i) are the final tristimulus values ​​of the i-th LED display module in the CIE1931 color space, X n 、Y n, Z n The X, Y, and Z components of the white field stimulus when the CIE standard illuminant illuminates a perfect diffuse reflector and then reflects to the observer's eyes through perfect diffuse reflection; f(ω) is a piecewise function;

[0020] Calculate the chromaticity difference of the LED display module according to the following formula

[0021]

[0022] Where, ΔL * Lightness L * The average brightness of all LED display modules in this batch The difference between * is chroma a * The average chromaticity of all LED display modules in this batch The difference between * is chroma b * The average chromaticity of all LED display modules in this batch The difference between .

[0023] Furthermore, for any LED display module, the final X, Y, and Z tristimulus values ​​of the CIE1931 color space are converted to the CIE-LAB uniform color space using the following formula to obtain the chromaticity a of the LED display module in the CIE-LAB uniform color space: * 、b * ;

[0024]

[0025]

[0026] Where FinX(i), FinY(i), and FinZ(i) are the final tristimulus values ​​of the i-th LED display module in the CIE1931 color space, X n 、Y n , Z n The X, Y, and Z components of the white field stimulus when the CIE standard illuminant illuminates a perfect diffuse reflector and then reflects to the observer's eyes through perfect diffuse reflection; f(ω) is a piecewise function;

[0027] Calculate the chromaticity difference of the LED display module according to the following formula

[0028]

[0029] Where Δa * is chroma a *The average chromaticity of all LED display modules in this batch The difference between * is chroma b * The average chromaticity of all LED display modules in this batch The difference between .

[0030] The transformation matrix of the X, Y, and Z components Obtained by the following method:

[0031] For each LED display module in a batch, use an area array camera to measure in a darkroom environment to obtain the measured tristimulus values ​​in the CIE1931 color space corresponding to the three primary colors of red, green, and blue; let the measured tristimulus values ​​in the CIE1931 color space corresponding to the single primary color of the i-th LED display module measured by the area array camera be CamX(i), CamY(i), and CamZ(i); when measuring the X, Y, and Z components of the measured tristimulus values, place an X filter, a Y filter, and a Z filter in front of the area array camera lens, respectively; use a luminance meter to measure the measured tristimulus values ​​in the CIE1931 color space corresponding to the red, green, and blue primary colors of each LED display module in the batch; let the measured tristimulus values ​​in the CIE1931 color space corresponding to the single primary color of the i-th LED display module measured by the luminance meter be MetX(i), MetY(i), and MetZ(i), and use the following formula to calculate the conversion matrix corresponding to the X, Y, and Z components;

[0032]

[0033]

[0034]

[0035] are the conversion matrices of the X, Y, and Z components respectively, and N is the number of LED display modules in this batch.

[0036] The transformation matrix of the X, Y, and Z components Obtained by the following method:

[0037] For each LED display module of a batch, a face array camera is used to measure in a darkroom environment to obtain the corresponding CIE1931 color space measured tristimulus value of blue; the CIE1931 color space measured tristimulus value corresponding to the i-th LED display module measured by the face array camera is CamX(i), CamY(i), and CamZ(i); when measuring the X, Y, and Z components of the measured tristimulus value, an X filter, a Y filter, and a Z filter are respectively placed in front of the lens of the face array camera; a luminance meter is used to measure the corresponding CIE1931 color space measured tristimulus value of blue of each LED display module of the batch; the CIE1931 color space measured tristimulus value corresponding to the i-th LED display module measured by the luminance meter is MetX(i), MetY(i), and MetZ(i), and the conversion matrix corresponding to the X, Y, and Z components is calculated by using the following formula:

[0038]

[0039]

[0040]

[0041] The conversion matrix of the X, Y, and Z components, respectively, and N is the number of LED display modules of the batch.

[0042] Beneficial effects: the present application can select display modules with chromaticity difference in a batch of LED display modules, screen out the display modules, and then splice the remaining display modules after luminance correction into a module, a box, or a display screen, which saves one-third of the time for chromaticity correction and does not cause color gamut loss, and can effectively weaken the uneven distribution of chromaticity after the display screen is lighted. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a flowchart of the present application. DETAILED DESCRIPTION

[0044] The present application will be further described in detail below in combination with the drawings and embodiments, and it can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.

[0045] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0046] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," or "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," or "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0047] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are used to refer to positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must be oriented, constructed, or operated in a specific manner. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0048] Example 1

[0049] The chromaticity difference screening method of the LED display module of the present invention is as follows:

[0050] Because the brightness meter is high in cost, slow in measurement and not suitable for long-term use in engineering, the present application selects a plane array camera to replace the brightness meter to measure each LED display module in a batch in a darkroom environment to obtain the measured tristimulus values of the three primary colors of each LED display module in CIE1931 color space; for any primary color, the measured tristimulus values of the CIE1931 color space of the i th LED display module measured by the plane array camera are CamX(i), CamY(i) and CamZ(i); when measuring the X, Y and Z components of the measured tristimulus values, an X filter, a Y filter and a Z filter are respectively placed in front of the lens of the plane array camera. Due to the optical vignetting effect of the plane array camera itself, the edge illumination of the image is reduced, the optical axis of the plane array camera needs to be aligned with the center area of the LED display module, and only the field center of the plane array camera is used to avoid the influence of the vignetting of the plane array camera, or the plane array camera is used after being corrected. The measured tristimulus values of the three primary colors of each LED display module in the batch in CIE1931 color space are measured by the brightness meter; the measured tristimulus values of the CIE1931 color space of the i th LED display module measured by the brightness meter are MetX(i), MetY(i) and MetZ(i), and the conversion matrix corresponding to the X, Y and Z components is calculated by using the following formula:

[0051]

[0052]

[0053]

[0054] The conversion matrix of the X, Y and Z components, and N is the number of the LED display modules in the batch.

[0055] For the LED display modules in the batch or other batches of LED display modules with the same pitch, the final tristimulus values FinX(i), FinY(i) and FinZ(i) in CIE1931 color space can be obtained by using the following formula; for other batches of LED display modules, the plane array camera should be measured under the same parameter conditions.

[0056]

[0057]

[0058]

[0059] The CIE1931 color space is a non-uniform color space, so the final tristimulus values ​​FinX(i), FinY(i), and FinZ(i) in the CIE1931 color space are converted to the CIE-LAB or CIE-Luv uniform color space. Here, taking the CIE-LAB uniform color space as an example, the following formula is used to convert it to the CIE-LAB uniform color space to obtain the lightness L of the LED display module in the CIE-LAB uniform color space. * and chroma a * 、b * ;

[0060]

[0061]

[0062] Where, X n 、Y n , Z n The X, Y, and Z components of the white field stimulus when the CIE standard illuminant illuminates a perfect diffuse reflector and then reflects to the observer's eyes through perfect diffuse reflection; f(ω) is a piecewise function;

[0063] Calculate the brightness L of all LED display modules in this batch * The mean Chroma a * The mean Chroma b * The mean

[0064] For any LED display module, calculate its brightness L * and lightness mean The difference between ΔL * 、chroma * and chromaticity mean The difference Δa * , chroma b * and chromaticity mean The difference Δb * ; Then calculate the chromaticity difference of the LED display module according to the following formula

[0065]

[0066] For a certain LED display module, if the chromaticity difference corresponding to any primary color is greater than or equal to the set chromaticity difference threshold, the LED display module is determined to have chromaticity difference and is screened out. The LED display modules less than the chromaticity difference threshold are corrected in brightness (the correction in brightness is usually performed in a module or a box for saving time), and then spliced into a display screen. According to the visual characteristics of human eyes, the chromaticity difference threshold is usually set to 6, and the chromaticity difference threshold can be set to 3-6 for a display screen with higher display quality requirements.

[0067] In Embodiment 2, it is known from Macadam ellipses that the CIE-XYZ chromaticity diagram is not very uniform, and the ability of human eyes to distinguish colors at different positions is greatly different, with the smallest in the blue part. Embodiment 2 is different from Embodiment 1 in that the measured tristimulus values of the CIE1931 color space corresponding to red and green are not measured, only the measured tristimulus values of the CIE1931 color space corresponding to blue are measured, and finally the chromaticity difference of the blue corresponding to each LED display module is calculated, so that the LED display modules with chromaticity difference are selected, one third of the time is saved, and basically the same effect can be achieved.

[0068] Embodiment 3

[0069] Since the brightness will change after correction, and the main purpose of the present application is to select the LED display modules with chromaticity difference, only the difference in saturation can be compared, therefore Embodiment 3 is different from Embodiments 1 and 2 in that the lightness difference ΔL * is not calculated, only the chromaticity difference Δa * and Δb * are calculated; and the chromaticity difference of the LED display module can be calculated according to the following formula .

[0070]

[0071] Embodiment 4

[0072] Human eyes can only distinguish the color difference between one LED display module and surrounding LED display modules, for example, the color difference between two LED display modules and the average of all LED display modules is very large, but the color difference between the two LED display modules is small, and human eyes cannot distinguish the difference. In this embodiment, the LED display modules used for splicing one are taken as a batch of modules, and the LED display modules with chromaticity difference are selected from the modules.

[0073] If the arrangement order of the LED display modules in the module is known, any LED display module and the surrounding display modules can be taken as a batch of modules, and the color difference of the module is calculated.

[0074] This embodiment is more in line with the characteristics of human eyes.

[0075] In Examples 1-4, LED display modules that have not been brightness corrected are selected, LED display modules with chromaticity differences are selected and filtered out, and the remaining LED display modules are spliced ​​into modules or boxes, and then brightness correction is performed on the modules or boxes as units, and finally the display screen is spliced.

[0076] The present invention can also first perform brightness calibration on each LED display module, and then screen and eliminate those with chromaticity differences. The remaining LED display modules can then be assembled into a screen. However, since calibration is performed on individual LED display modules, it takes a certain amount of time, but the display effect is better.

Claims

1. A method for screening chromaticity differences of LED display modules, characterized in that The method is as follows: For each LED display module in a batch, use an area scan camera to measure its CIE1931 color space tristimulus values ​​in a darkroom. When measuring the X, Y, and Z values ​​of the tristimulus values, place an X filter, a Y filter, and a Z filter in front of the area scan camera lens, respectively. The final X, Y, and Z tristimulus values ​​in the CIE1931 color space are calculated using the following formula: Wherein, FinX(i), FinY(i), and FinZ(i) are the final X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space; CamX(i), CamY(i), and CamZ(i) are the actual X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space measured by the area array camera; i = 1, 2…, N, where N is the number of LED display modules in this batch. are the transformation matrices of the X, Y, and Z components respectively; Convert the final X, Y, and Z tristimulus values ​​of the CIE1931 color space of each LED display module to a uniform color space, and calculate the chromaticity difference of each LED display module in the uniform color space; filter out LED display modules in the batch whose chromaticity difference is greater than or equal to a set chromaticity difference threshold; For each LED display module, use an area array camera to measure in a darkroom when displaying red, green, and blue at its highest grayscale, obtaining the measured tristimulus values ​​in the CIE1931 color space corresponding to the red, green, and blue primary colors. Alternatively, use an area array camera to measure in a darkroom when displaying only blue at its highest grayscale, obtaining the measured tristimulus values ​​in the CIE1931 color space corresponding to the blue primary color. For any LED display module, the final X, Y, and Z tristimulus values ​​of the CIE1931 color space are converted to the CIE-LAB uniform color space using the following formula to obtain the lightness L of the LED display module in the CIE-LAB uniform color space: * and chroma a * 、b * ; Where FinX(i), FinY(i), and FinZ(i) are the final tristimulus values ​​of the i-th LED display module in the CIE1931 color space, X n 、Y n , Z n The X, Y, and Z components of the white field stimulus when the CIE standard illuminant illuminates a perfect diffuse reflector and then reflects to the observer's eyes through perfect diffuse reflection; f(ω) is a piecewise function; Calculate the chromaticity difference of the LED display module according to the following formula Where, ΔL * Lightness L * The average brightness of all LED display modules in this batch The difference between * is chroma a * The average chromaticity of all LED display modules in this batch The difference between * is chroma b * The average chromaticity of all LED display modules in this batch The difference between .

2. A method for screening chromaticity differences of LED display modules, characterized in that The method is as follows: For each LED display module in a batch, use an area scan camera to measure its CIE1931 color space tristimulus values ​​in a darkroom. When measuring the X, Y, and Z values ​​of the tristimulus values, place an X filter, a Y filter, and a Z filter in front of the area scan camera lens, respectively. The final X, Y, and Z tristimulus values ​​in the CIE1931 color space are calculated using the following formula: Wherein, FinX(i), FinY(i), and FinZ(i) are the final X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space; CamX(i), CamY(i), and CamZ(i) are the actual X, Y, and Z tristimulus values ​​of the i-th LED display module in the CIE1931 color space measured by the area array camera; i = 1, 2…, N, where N is the number of LED display modules in this batch. are the transformation matrices of the X, Y, and Z components respectively; Convert the final X, Y, and Z tristimulus values ​​of the CIE1931 color space of each LED display module to a uniform color space, and calculate the chromaticity difference of each LED display module in the uniform color space; filter out LED display modules in the batch whose chromaticity difference is greater than or equal to a set chromaticity difference threshold; For each LED display module, use an area array camera to measure in a darkroom when displaying red, green, and blue at its highest grayscale, obtaining the measured tristimulus values ​​in the CIE1931 color space corresponding to the red, green, and blue primary colors. Alternatively, use an area array camera to measure in a darkroom when displaying only blue at its highest grayscale, obtaining the measured tristimulus values ​​in the CIE1931 color space corresponding to the blue primary color. For any LED display module, the following formula is used to convert the final X, Y, and Z tristimulus values ​​of the CIE1931 color space to the CIE-LAB uniform color space to obtain the chromaticity a of the LED display module in the CIE-LAB uniform color space: * 、b * ; Where FinX(i), FinY(i), and FinZ(i) are the final tristimulus values ​​of the i-th LED display module in the CIE1931 color space, X n 、Y n , Z n The X, Y, and Z components of the white field stimulus when the CIE standard illuminant illuminates a perfect diffuse reflector and then reflects to the observer's eyes through perfect diffuse reflection; f(ω) is a piecewise function; Calculate the chromaticity difference of the LED display module according to the following formula Where Δa * is chroma a * The average chromaticity of all LED display modules in this batch The difference between * is chroma b * The average chromaticity of all LED display modules in this batch The difference between .

3. The method for screening chromaticity differences of LED display modules according to claim 1 or 2, wherein: Multiple LED display modules used to splice a module, a cabinet or a display screen constitute a batch of LED display modules.

4. The method for screening chromaticity differences of LED display modules according to claim 1 or 2, wherein: The LED display module in a module and its surrounding LED display modules together constitute a batch of LED display modules.

5. The method for screening chromaticity differences of LED display modules according to claim 1 or 2, characterized in that: The transformation matrix of the X, Y, and Z components Obtained by the following method: For each LED display module in a batch, use an area array camera to measure in a darkroom environment to obtain the CIE1931 color space measured tristimulus values ​​corresponding to the three primary colors of red, green, and blue; let the CIE1931 color space measured tristimulus values ​​corresponding to the i-th LED display module measured by the single-primary area array camera be CamX(i), CamY(i), and CamZ(i); when measuring the X, Y, and Z components of the tristimulus values, place an X filter, a Y filter, and a Z filter in front of the area array camera lens, respectively; use a luminance meter to measure the CIE1931 color space measured tristimulus values ​​corresponding to the red, green, and blue primary colors of each LED display module in the batch; let the CIE1931 color space measured tristimulus values ​​corresponding to the single-primary color of the i-th LED display module measured by the luminance meter be MetX(i), MetY(i), and MetZ(i), and use the following formula to calculate the conversion matrix corresponding to the X, Y, and Z components; are the conversion matrices of the X, Y, and Z components respectively, and N is the number of LED display modules in this batch.

6. The method for screening chromaticity differences of LED display modules according to claim 1 or 2, characterized in that: The transformation matrix of the X, Y, and Z components Obtained by the following method: For each LED display module in a batch, use an area array camera to measure in a darkroom environment to obtain the CIE1931 color space measured tristimulus values ​​corresponding to blue. Let the CIE1931 color space measured tristimulus values ​​corresponding to the i-th LED display module measured by the area array camera be CamX(i), CamY(i), and CamZ(i). When measuring the X, Y, and Z components of the measured tristimulus values, place an X filter, a Y filter, and a Z filter in front of the area array camera lens, respectively. Use a luminance meter to measure the CIE1931 color space measured tristimulus values ​​corresponding to the blue of each LED display module in the batch. Let the CIE1931 color space measured tristimulus values ​​corresponding to the i-th LED display module measured by the luminance meter be MetX(i), MetY(i), and MetZ(i). Use the following formula to calculate the conversion matrix corresponding to the X, Y, and Z components. are the conversion matrices of the X, Y, and Z components respectively, and N is the number of LED display modules in this batch.

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