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Analysis of evaluation standards for small pitch LED screens

Author：admin / Publication time：2023-10-25

A qualified and reliable small pitch LED display screen must undergo strict relevant testing before leaving the factory. Only in this way can a considerable amount of normal operation and good display effect be guaranteed and the failure rate be reduced after the customer's formal delivery and use. Let's take a look at the evaluation standards and methods for small pitch LED display screens by administrative unit purchasers.

Test methods and conditions for small pitch LED display screens

Equipment: 1 Blu ray high-definition player with a resolution of 1080P (1920) x 1080 full frames; 1 high-performance computer with 1080PHDMI output; 1 video signal distributor with 1080PHDMI output.

(2) Standard video source, image testing: Blu ray source disk; Professional testing video Hi DefinitionReference (selecting multiple scenarios); DisplayX, SJ light-emitting diode/T11281-2007 (LED) standard testing software display testing methods; Computer generated 1080P standard color scale, full color gradient, gray scale and pictures from the Internet, as well as the above two intercepted or generated pictures, as well as road bridge night pictures.

(3) Testing method: Before formal evaluation, each manufacturer is allowed to conduct multiple on-site debugging on their LED/large screens (due to limited site size, it is recommended to refer to the resolution of the splicing screen as 720P or 1080P line) to achieve the best results of their respective products. Starting from the designated time, the review team is composed of multiple experts with rich experience in image transmission, video display, and LED large screen hardware to evaluate the actual application effects.

The second is the evaluation requirements for small pitch LED displays

Grayscale Image Test (1)

① Grayscale and color scale testing has always been an important indicator reference for large screens or splicing large screens, such as DLP/plasma/LCD/LED, used to evaluate the grayscale transition ability and black and white conversion ability of large screen splicing and controllers (if any). The more obvious the contrast, the stronger the display system's ability to process color images.

The bidirectional grayscale signal is used to test the minimum 16 grayscale levels that the system should display. Each level can be distinguished, earning 3 points; If you differentiate a level, you will receive 1 point, and the lowest score for this project is 0.

On the screen, a 252 level grayscale image should be able to simultaneously distinguish the three darkest grayscale A B、C， And the three brightest gray scales U, V, and W. A, B, and C must have a sense of hierarchy and cannot appear black; Similarly, U, V, and w should also have a sense of hierarchy and not appear white. During playback, any large screen images with colored or off color will have points deducted. If there is no color difference (impure black and white, and other colors), 2 points will be added. If the color is biased, deduct 1 as appropriate 2 points.

② Comprehensive testing of clarity and grayscale. This scenario is used to comprehensively test the performance of the entire system, including line count, grayscale, geometric distortion, etc. 1080P (1920) x 1080) Each grayscale level and number of lines must be clear and distinguishable, and the black and white purity of the grayscale can also be tested. If there are any issues, reduce 1 point; 1 point minimum.

③ Grayscale realistic image. The more black and white levels are displayed, the better the grayscale processing ability of the system can be reflected. 2 points minimum and 5 points maximum.

(2) Color image testing

① Comprehensive testing of deep color images. This scene is a night scene, focusing on the changes in color brightness and halo intensity, used to test the system's performance in various aspects such as color, grayscale, and detail display. Can clearly distinguish the halo on the left ship under the bridge from the top of the main tower and the bridge deck cable, earning 4 points. If there is a problem, deduct 1 according to the severity 2 points. There is no problem distinguishing the brightness changes of other details, an additional point will be added.

② Bright detail test: a test of the ability to restore details based on bright white. This scene is a high brightness dining table and dressing table. The main test is the restoration ability of the white part of the system under high light and the dynamic range of the gray stage. The texture details of curtains, fabrics, brushes, and other objects should be fully preserved. All projects meet the requirements, 5 points. If it does not meet the requirements, 0.5 points will be deducted for each item, and a total of 2 points will be deducted.

③ Test the clarity of facial details. This scene is a close-up static image of a girl and a flower, reflecting the authenticity of the large screen splicing system for details such as facial skin tone and spots, as well as the authenticity of skin tone. A total score of 5 points, 0.5 points deducted for unclear facial details. Impure facial color, deduct 1 point.

④ Color restoration test. Mainly testing the uniformity of color and the purity of white. The various ingredients and fruit colors in the kitchen, the pure white crystals on the tray, the pen holders of colored pencils, the wood grain, and the restoration display of grasslands and clouds are very important. White is impure, deduct 1 according to the purity of the color deviation Three points. Full score of 5 points.

⑤ Color saturation and detail testing. The fuzz on the edge of the pile of yarn should be clearly visible, and the texture of the spool and padding should also be clear and distinguishable. Full score of 5 points. Unclear fuzz, deduct 1 point; Unclear texture of the spool, deduction of 1 point; The texture of the mat is not clear, deduct 1 point.

The third is dynamic scene testing

ROCK&WAVE, blue light source: 00014. m2ts. This scene is a sea reef scene used to test the image quality of the device in a stationary background with a large amount of motion, especially white balance and detail resolution. In addition, the fog (water mist) generated by waves between 20 and 27 seconds of playback should be clearly distinguished. 5 points is the maximum score. If the level of waves and reefs is unclear, 0.1 points will be deducted appropriately FOG display is unclear, deduct 0.5 appropriately 2 points.

① Light and dark detail testing (ToyoNight, blue light source: 00019. m2ts). This scene is a sporty image of Tokyo's night scene, mainly divided into four scenes: a tower under the lights; Christmas tree embedded with lights; Bridges and night views on both sides of the Taiwan Strait; The night view around the Ferris wheel. The main test is the color restoration ability and dynamic range of brightness contrast of the system during dynamic video playback. The mesh details, Christmas tree details, dark details on both sides of the bridge, bright parts of the Ferris wheel, and dark details in the neighborhood should be fully preserved in the bright neon lights. The minimum score is 2 points, and the maximum score is 5 points (if each detail and level is unclear, 0.1 to 1 point can be deducted as appropriate).

② Black&White comparison test (blue light source: 000200.m2ts). Mainly testing the edge resolution ability of black and white scenes and black and white dressed characters. Up to 5 points, the black background and the edges of black clothes can be clearly distinguished, earning 3 points. If the white background and the edges of white clothes can be clearly distinguished, score 2 points. If the edges of the same color are not clear, deduct 1 as appropriate 2 points.

③ Color expression: Accessories (blue light test source: 00021. m2ts). The main scenes are flowers and accessories (necklaces, gloves, feather accessories, etc.), Mainly testing the transparency of colors and the texture of objects. In addition, it is also important to display the small floating details of the feathers. Up to 5 points, if the level of flowers is not enough, 1 point will be deducted; If the details of the feathers are unclear, 1 point will be deducted; If the color is opaque, deduct 1 point.

④ Dark detail test (BlackImage blue light test source: 00027. m2ts). The more black and white levels are displayed, the better the system's ability to handle details in dark areas, and the higher the restored gray level can be displayed. Clear resolution of black layers, with a maximum score of 10 points; If the black part lacks sufficient layers, deduct 2 as appropriate 6 points.

I won't go into detail about the remaining tests.

DisplayX series professional software testing)

① Solid colors: Black, RGB, P (purple), Y, C (blue), White. The solid colors of black, white, and six other colors are displayed unevenly, with a total deduction of 0-1 points for year-on-year comparison. When there are bad points, 2 points will be deducted based on the bad points Three points, year-on-year comparison. Up to 5 points.

② Color and Grayscale: Gradient Test (No Polarization). R//gradually changes from left to right. G/B three color signal and Y/Pure/Cyan mixed with two colors are used to test the chromaticity and grayscale changes of the system. The gradient lacks a sense of step, meaning that the smoother the transition, the higher the grayscale level of the system. If each color is transparent without any faults or vertical steps, the maximum score for this is 5 points. The severity of different color levels will be deducted by 1 compared to the same period last year 3 points.

③ Full color gradient. Full spectrum gradient, no polarization changes, the more gorgeous the color, the better the transparency, and the less ideal the various internal strips. The evaluation must be deducted points accordingly; The closer the various displays are to the vertical, the better the synchronization of various grayscale changes. Gradually transparent, without faults or vertical stages, this is 4 points. During the gradient process, if there is no uneven color change, this project will receive 1 point. According to the severity of the color fault, 1-3 points will be deducted year-on-year.