A method for screening ink color in LED display products

Abstract

This invention relates to a method for screening the black color of LED display products. The method is as follows: The lighting angle of the light source is adjusted so that the light entering the color camera from the surface of the LED panel contains only diffuse reflection light; the LED panel is photographed with the color camera at a set exposure value to obtain an image of the LED panel; the differences in grayscale value L, red-green hue value A, and yellow-blue hue value B between different regions in the image's ROI area are calculated, and LED panels with differences less than g*k1, g*k2, and g*k3, respectively, are designated as OK substrates and placed in a storage area, where g is the defect gradient, and k1, k2, and k3 are set coefficients. This invention ensures a scientifically consistent screening standard, and compared with traditional human eye screening methods, the efficiency and effectiveness of black color screening are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of ink color screening technology for LED display products, and relates to a method for screening ink color in LED display products. Background Technology

[0002] In recent years, with the increasing demand for high-definition and high-resolution display quality, the pixel pitch of LED displays has gradually decreased, and the pixel size has been miniaturized. A large-size display screen needs to be spliced ​​together from multiple display unit modules, making the color consistency of LED displays a key issue for manufacturers. To address this problem, most industry players rely on visual inspection under specific conditions to screen and classify display modules. However, because people's color perception and sensitivity vary, this screening method is inconsistent, inefficient, and fails to yield satisfactory results. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a standardized, scientific and efficient method for screening the ink color of LED display products.

[0004] To solve the above-mentioned technical problems, the LED display product ink color selection method of the present invention is as follows:

[0005] Step 1: Fix the light source and color camera above the light panel at the set heights H1 and H2; adjust the lighting angle of the light source so that the light entering the color camera from the surface of the light panel contains only diffused light.

[0006] Step 2: Take a picture of the light panel using a color camera at the set exposure value EV to obtain an image of the light panel; calculate the difference d between the gray values ​​L of each region in the ROI area of ​​the image. L The difference d between red and green hue values ​​A A The difference d between the yellow and blue saturation values ​​B B and all d L d A d B Light boards smaller than g*k1, g*k2, and g*k3 respectively are placed in the storage area as OK substrates, where g is the defect gradient and k1, k2, and k3 are set coefficients.

[0007] Furthermore, the present invention also includes step three: calculating the average grayscale value of all partitions of each OK substrate in the storage area. Average red-green color value and the average value of yellow-blue saturation Then calculate the distance between each OK substrate The difference The difference The difference Select OK substrates smaller than k1, k2, and k3 respectively are used for secondary module splicing.

[0008] The light source is preferably a strip light source.

[0009] The red-green hue value A is the average of the red hue value and the green hue value of the partition, and the yellow-blue hue value B is the average of the yellow hue value and the blue hue value of the partition.

[0010] The image ROI region is a rectangular area with the edges of the light panel image removed.

[0011] The image ROI region is divided into 2-6 partitions.

[0012] Furthermore, k1 = 0.1 ± 0.02, k2 = 0.6 ± 0.02, and k3 = 0.6 ± 0.02.

[0013] For light panels with different dot spacing, the undesirable gradient g and the exposure value EV of the color camera are calibrated in advance under the same conditions as in step one.

[0014] For a light panel with a dot pitch of 1.58, the defect gradient g is 25-28, and the exposure value EV is 31000-35000.

[0015] Beneficial effects: This invention has been verified through hundreds of experiments, ensuring that the screening criteria are scientific and consistent. Compared with the traditional human eye screening method, the efficiency and effectiveness of ink screening are greatly improved. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the relative positions of the camera, light source, and the lamp board under test in this invention.

[0017] Figure 2 It is a photo of the light panel containing three parameters obtained after testing.

[0018] Figure 3 These are photos of LED displays that have been built using traditional human visual filtering.

[0019] Figure 4 These are photos of LED displays constructed using the methods described in this invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the drawings, not the entire structure.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0024] The LED display product ink color screening method of the present invention includes the following steps:

[0025] Step 1: As Figure 1 As shown, the light panel 1, light source 2, and color camera 3 are fixed at the bottom, middle, and top positions respectively, ensuring that the distance between them is at the set height. In this embodiment, a strip light source is used, with the height of the light source from the surface of the light panel H1 = 12cm and the height of the color camera lens from the surface of the light panel H2 = 17cm. A CMOS color camera is used. A white ring light source or a surface light source can also be used, but subsequent adjustments to the lighting angle will be more complicated.

[0026] Adjust the lighting angle of the light source to minimize light entering the camera lens through mirror reflection, thereby more accurately distinguishing the uniformity of ink color on the surface of the light panel.

[0027] Step 2: Take a picture of the light panel surface with a color camera at the set exposure value EV to obtain the light panel image; in order to eliminate the light panel edges that may contain specular reflections from strip light sources, define the ROI region (i.e., region of interest, which is a rectangle slightly smaller than the size of the light panel to be tested) for images of light panels of different sizes; detect the uniformity of ink color on the surface of the ROI region, and filter and classify based on the gray value L as the main basis. In addition, because there are different background colors on the light panel surface, red-green value A and yellow-blue value B are introduced to further correct the filtering results, where red-green value A is the average of red value and green value, and yellow-blue value B is the average of yellow value and blue value.

[0028] The ROI area is divided into multiple partitions, which can be 2 to 6 partitions depending on the size of the light panel. For example... Figure 2 Taking four partitions as an example, when the difference d between the grayscale values ​​L of the four partitions is... L The difference d between red and green hue values ​​A A The difference d between the yellow and blue saturation values ​​B B When the values ​​are less than g*k1, g*k2, and g*k3 respectively, the light board is considered an OK substrate that has passed the initial screening and is placed in the storage area; otherwise, it is discharged as an NG substrate and does not enter the storage area. Here, g is a pre-defined defect gradient; k1, k2, and k3 are set coefficients, k1 = 0.1 ± 0.02, k2 = 0.6 ± 0.02, and k3 = 0.6 ± 0.02. Simultaneously, the software calculates and records the average grayscale value L of the four zones for each OK substrate. The average value of red-green hue A The average value of yellow-blue saturation B

[0029] Step 3: Once the number of light boards (OK substrates) in the storage area reaches the preset quantity, the software calculates the relationship between each OK substrate. The difference The difference The difference Select OK substrates smaller than k1, k2, and k3 are used for secondary module splicing; the selected 6 or 12 OK substrates are spliced ​​manually or with a nailing machine into secondary modules, and these secondary modules are further spliced ​​into a large-size display screen. Figure 4 It can be seen that the display screen with uniform ink color obtained by this method is significantly better than that of a display screen built using traditional methods. Figure 3 It has obvious advantages.

[0030] Taking a light panel with a dot pitch of 1.58 as an example, the method for calibrating the defective gradient g and the color camera exposure value is as follows:

[0031] Step 1: Fix the light panel 1, light source 2, and color camera 3 at the bottom, middle, and top positions respectively. The height of the light source from the surface of the light panel is H1 = 12cm, and the height of the color camera lens from the surface of the light panel is H2 = 17cm. A CMOS color camera is used, and a strip light source is used. Adjust the lighting angle of the light source so that the light entering the color camera from the surface of the light panel contains only diffused light.

[0032] Step 2: Set provisional values ​​for the exposure value EV and the defect gradient g. Use a color camera to take a picture of the light panel surface at the set exposure value EV to obtain an image of the light panel. Divide the ROI region of the light panel image into four equal parts. When the difference d between the gray values ​​L of the four parts is... L The difference d between red and green hue values ​​A A The difference d between the yellow and blue saturation values ​​B B When the values ​​are less than g*k1, g*k2, and g*k3 respectively, the light board is considered a qualified OK substrate that has passed the initial screening and is placed in the storage area; k1 = 0.1 ± 0.02, k2 = 0.6 ± 0.02, k3 = 0.6 ± 0.02. Simultaneously, the software records the average grayscale value L of the four zones for each OK substrate. The average value of red-green hue A The average value of yellow-blue saturation B

[0033] Step 3: Once the number of LED light boards (OK substrates) in the storage area reaches the preset quantity, the software calculates the relationship between each OK substrate. The difference The difference The difference Select OK substrates smaller than k1, k2, and k3 are used for secondary module splicing; the selected 6 or 12 OK substrates are spliced ​​into secondary modules by manual or nailing machine, and then these secondary modules are further spliced ​​into a large-size display screen.

[0034] Observe the splicing effect of the display screen. If the color uniformity is not ideal, adjust the provisional values ​​of the exposure value EV and the poor gradient g, and repeat steps 1-3 until a display screen with ideal color uniformity is spliced. Use the exposure value EV and the poor gradient g determined at this time as the calibration values ​​corresponding to the light panel with that dot pitch.

[0035] After multiple tests, it was determined that for a light panel with a pixel pitch of 1.58, the optimal defect gradient is 25-28, the camera exposure value EV = 31000-35000, and the spliced ​​display screen has a better consistency in ink color.

[0036] This invention is not limited to the embodiments described above. Depending on the actual situation and the desired photographic effect, the height values ​​of the color camera and light source from the lamp panel surface described above can be selected, and the camera's shooting angle may not be perpendicular to the lamp panel surface. Based on the hints and guidance in the above specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, this invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to this invention should also fall within the protection scope of the claims of this invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this invention.

Claims

1. A method of LED display product ink color screening, characterized in that The method is as follows: Step one, the light source, color camera according to the set height H1, H2 fixed in the light plate above; adjust the light source angle, so that the light from the light plate surface into the color camera only contains diffuse reflection light; Step two, take a picture of the lamp panel with a color camera at a set exposure value EV to obtain a lamp panel image; calculate the difference d of the gray value L between each sub-area in the ROI region of the image L , the difference d of the red-green chroma value A A , the difference d of the yellow-blue chroma value B B , and all d L , d A , d B are less than g*k1, g*k2, g*k3 respectively, and the lamp panel is put into the storage area as an OK substrate, wherein g is a bad gradient, and k1, k2, k3 are set coefficients; Step three: calculate the average value of the gray value of each OK substrate in each partition of the storage area The average value of red-green chroma value And the average value of yellow-blue chroma value Recalculate the difference between each OK substrate The difference between The difference between The difference between Select OK substrate less than k1, k2, k3 respectively for secondary module splicing.

2. The LED display product ink color screening method according to claim 1, characterized in that The light source is a bar light source.

3. The LED display product ink screening method according to claim 1, wherein The red-green chroma value A is the average value of the partitioned red chroma value and green chroma value, and the yellow-blue chroma value B is the average value of the partitioned yellow chroma value and blue chroma value.

4. The LED display product ink screening method of claim 1, wherein The image ROI region is a rectangular region excluding the edge of the light plate image.

5. The LED display product ink screening method of claim 1, wherein The image ROI region is equally divided into 2-6 partitions.

6. The LED display product ink screening method of claim 1, wherein k1=0.1±0.02, k2=0.6±0.02, k3=0.6±0.

02.

7. The LED display product ink screening method of claim 1, wherein For different point spacing light plates, the bad gradient g and the exposure value EV of the color camera are calibrated in the same conditions as step one.

8. The LED display product ink screening method of claim 1, wherein For the light plate with a point spacing of 1.58, the bad gradient g is 25-28, and the exposure value EV is 31000-35000.

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