At present, transparent LED screen display is in the factory situation, and the cost is not cheap. Although the theoretical life span is 100,000 hours, in fact, after about 5,000 to 10,000 hours of operation, the uniformity will deteriorate, start to become flowery, and the commercial value will decrease. After 15,000 to 20,000 hours, the commercial value is almost lost, resulting in a huge waste of social resources.
Therefore, whether before leaving our factory or after using it for a period of time, the point-by-point correction technology can greatly improve the uniformity of the display screen in a very short time and at a very low cost, and significantly improve the image quality.
Before being applied to the factory, point-by-point correction is a means of quality improvement, which means the improvement of competitiveness and the expansion of profit margins; after being used for a period of time, point-by-point correction can prolong the display effect of the full-color LED display, which is beneficial for users. Create more business value and reduce waste of resources.
There are two main types of mainstream point-by-point correction techniques:
1. On-site point-by-point correction of transparent LED screen display
It is to operate the entire large screen that should be installed. Due to the influence of the environment, weather and technical compatibility problems in different places, the correction cost is high, especially the maintenance of some foreign orders.
2. LED cabinet calibration point by point of transparent glass LED Screen
At present, LED display manufacturers use cabinet-by-point calibration, which is a test procedure that must be passed before the LED transparent screen leaves the factory. dreamroad LEDs’ cabinet calibration technology is at the forefront of the industry, and the transparent screen has strong adaptability to various environments. The display effect is consistent.
The following focuses on the point-by-point calibration of the cabinet:
Cabinet calibration is the last step before leaving the factory. It is mainly used to eliminate the brightness and chromaticity differences between the cabinet and the cabinet, and improve the uniformity of the LED display after splicing.
In addition to adding calibration steps in the production process,we generally need to follow up on the calibration effect of the screen cabinet when it leaves the factory.
There are three commonly used methods:
First is to splicing all the cabinets together to observe the display effect, but the workload of splicing is relatively large, which is inconvenient to realize;
Second is to randomly select some cabinets for splicing and observe the correction effect;
Third is to use the measurement data recorded by the calibration system to simulate and evaluate the calibration effect of all cabinets. Added LED production lines for cabinet calibration and simulation evaluation/sampling inspection.
Similar to on-site calibration, for each cabinet, the process of cabinet calibration includes data acquisition, data analysis, target value setting, correction coefficient calculation and coefficient upload, and also requires the cooperation of the control system.
Key technologies and difficulties:
Cabinet calibration is an effective way to improve the image quality of LED transparent screen, and its key technical aspects are mainly reflected in the following two aspects:
1. Inter-pixel uniformity inside the cabinet
Including light and chromaticity uniformity correction and light/dark line correction:
Brightness and chromaticity uniformity correction:
The brightness and chromaticity information of each LED lamp in the LED cabinet is measured by measuring equipment. The measurement method involves the knowledge of photometry, chromaticity and digital image processing; after obtaining the chromaticity information of each LEDs, the corresponding calibration standard, calculate the corresponding correction coefficient and send it to the receiving card of the corresponding cabinet; after the cabinet is lit, the display control system will adjust the LED current according to the correction coefficient, so that the brightness and chromaticity of all LEDs in the cabinet are consistent.
Bright and dark line correction:
It is to adjust the fluctuating LED brightness to a consistent lervel. In the process of adjusting the brightness, it is necessary to appropriately reduce the maximum brightness value of most LEDs.
Chromaticity correction is based on the principle of RGB color matching, and solves the problem of chromaticity deviation by changing the color coordinates of RGB three colors. For the color gamut comparison diagram before and after correction, the large triangle is the color gamut of the display screen before correction, and RGB three colors.
The color coordinates are discretely distributed; the small triangle is the corrected color gamut of the display screen, and the RGB three-color color coordinates are consistent.
Due to the limitations of machining accuracy, assembly accuracy and other technological reasons, there is a slight inconsistency in the spacing of the spliced LED module, and bright lines or dark lines will appear during turned on.
2. Brightness and chromaticity consistency between cabinets
The human eye can only distinguish the brightness difference of more than 4-5% between LED pixels, but can easily identify the 1% difference in the brightness and chromaticity of the cabinet.
That is to say, the human eye has lower requirements on the consistency of the pixels inside the cabinet, but higher requirements on the consistency between the cabinets. Therefore, the consistency of brightness and chromaticity between cabinets is a key technology unique to cabinet calibration.
The inconsistency of brightness and chromaticity between cabinets is mainly reflected in two aspects:
(1) There is a difference in the average brightness and chromaticity between the cabinets.
When the cabinets are spliced, a clear boundary line will appear, which can be achieved by adjusting the color gamut and setting the appropriate target value; if necessary, it is necessary to equip the precision A higher colorimeter for auxiliary measurements.
(2) The brightness and chromaticity distribution of the cabinet presents a gradient distribution, which is caused by the existence of a gradient distribution phenomenon in the measurement data of the cabinet.
When the cabinets are spliced together, the brightness of the splicing place will undergo a large jump, forming an obvious splicing line. This requires the correction system to be able to detect and resolve the gradient distribution of the measurement data.
