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Talking about the processing technology of LED display chromaticity
by：Demo
2021-07-10
LED display technology has ranged from monochrome displays in the early 1980s, to dual-primary color displays in the late 1980s, to three-primary (full-color) displays in the mid-1990s, and we have been widely used in the flat panel display field today. Discussed multi-primary color (greater than three primary colors) processing technology. The chromaticity processing technology of the LED display screen ranges from the most basic wavelength selection of the primary color, to the adjustment of the white field color temperature, to the color space conversion processing to improve the color reproduction, and the chromaticity uniformity processing to improve the image quality. Today we have adopted multi-primary color (greater than three primary colors) processing in order to expand the color gamut and reproduce more natural colors. Various chromaticity processing technologies run through the development history of LED display screens and become one of the most core technologies in the comprehensive discipline of LED display screens.
The choice of primary color wavelength
LED display screens are widely used in various industries, and different applications have different requirements for the wavelength of the primary color of the LED. Some of the wavelengths of the primary color of the LED are selected for good visual effects, and some are for It conforms to people's habits, and some of them are regulated by industry standards, national standards and even international standards. For example, the choice of the wavelength of the primary color of the green tube in the full-color LED display; in the early days, the yellow-green LED with a wavelength of 570nm was generally used. Although the cost is lower, the color gamut of the display is small, the color reproduction is poor, and the brightness is low. After choosing a pure green tube with a wavelength of 525nm, the color gamut of the display screen has nearly doubled, and the color reproduction has been greatly improved, which greatly improves the visual effect of the display screen. For another example, on the stock market display screen, people are usually accustomed to using red to indicate rising stock prices, green to indicate falling stock prices, and yellow to indicate flat prices. In the transportation industry, the national standards strictly stipulate that the blue and green bands are for traffic and the red band is forbidden. Therefore, the choice of primary color wavelength is one of the important links of LED display screens.
Adjustment of white field color coordinates
White field color coordinate adjustment is one of the most basic technologies for full-color LED displays. However, in the mid-1990s, due to the lack of industry standards and basic testing methods, the white field color coordinates were usually determined by human eyes and feelings, resulting in serious color cast and random white field color temperature. With the promulgation of industry standards and the completion of testing methods, many manufacturers have begun to standardize the color matching process for full-color screens. However, due to the lack of theoretical guidance for color matching, some manufacturers often sacrifice the gray levels of certain primary colors to adjust the 100-field color coordinates, and the overall performance cannot be improved.
Chromaticity uniformity treatment
The chromaticity uniformity of LED display screens has always been a major problem that plagued the industry. It is generally believed that the uneven brightness of LEDs can be corrected by a single point to improve the brightness uniformity. The uneven chromaticity cannot be corrected and can only be improved by subdividing and filtering the LED color coordinates.
As people's requirements for LED displays are getting higher and higher, only subdividing and filtering the color coordinates of LEDs can no longer satisfy people's picky eyes. Comprehensive correction of the display can improve the chromaticity uniformity. It is achievable.
We found that even the same grade of LEDs of the world's first brand has a large wavelength deviation and color saturation deviation, and the deviation range greatly exceeds the threshold value of the human eye for the discrimination of green color difference. Therefore, the color uniformity correction is carried out. It is of great significance.
In the CIE1931 chromaticity diagram, according to the law of the center of gravity, we found that: at any point in the G file range (u0026Square; abcd) mixed with a certain proportion of red and blue, the color coordinates of the mixed color can be adjusted To the intersection O of the straight line cR and the straight line dB.
Although the chromaticity uniformity can be greatly improved. However, the color saturation after correction is significantly reduced. At the same time, another prerequisite for the use of red and blue to correct the uniformity of green chromaticity is that the three types of red, green and blue LEDs in the same pixel should be distributed as closely as possible to make the mixing distance of red, green and blue as close as possible to achieve better results. Effect. At present, the LED uniform distribution method is commonly used in the industry, which will bring confusion to the chromaticity uniformity correction. In addition, how to measure the color coordinates of tens of thousands of red, green and blue LEDs is also an extremely difficult problem. We gave a hint about this.
The choice of primary color wavelength
LED display screens are widely used in various industries, and different applications have different requirements for the wavelength of the primary color of the LED. Some of the wavelengths of the primary color of the LED are selected for good visual effects, and some are for It conforms to people's habits, and some of them are regulated by industry standards, national standards and even international standards. For example, the choice of the wavelength of the primary color of the green tube in the full-color LED display; in the early days, the yellow-green LED with a wavelength of 570nm was generally used. Although the cost is lower, the color gamut of the display is small, the color reproduction is poor, and the brightness is low. After choosing a pure green tube with a wavelength of 525nm, the color gamut of the display screen has nearly doubled, and the color reproduction has been greatly improved, which greatly improves the visual effect of the display screen. For another example, on the stock market display screen, people are usually accustomed to using red to indicate rising stock prices, green to indicate falling stock prices, and yellow to indicate flat prices. In the transportation industry, the national standards strictly stipulate that the blue and green bands are for traffic and the red band is forbidden. Therefore, the choice of primary color wavelength is one of the important links of LED display screens.
Adjustment of white field color coordinates
White field color coordinate adjustment is one of the most basic technologies for full-color LED displays. However, in the mid-1990s, due to the lack of industry standards and basic testing methods, the white field color coordinates were usually determined by human eyes and feelings, resulting in serious color cast and random white field color temperature. With the promulgation of industry standards and the completion of testing methods, many manufacturers have begun to standardize the color matching process for full-color screens. However, due to the lack of theoretical guidance for color matching, some manufacturers often sacrifice the gray levels of certain primary colors to adjust the 100-field color coordinates, and the overall performance cannot be improved.
Chromaticity uniformity treatment
The chromaticity uniformity of LED display screens has always been a major problem that plagued the industry. It is generally believed that the uneven brightness of LEDs can be corrected by a single point to improve the brightness uniformity. The uneven chromaticity cannot be corrected and can only be improved by subdividing and filtering the LED color coordinates.
As people's requirements for LED displays are getting higher and higher, only subdividing and filtering the color coordinates of LEDs can no longer satisfy people's picky eyes. Comprehensive correction of the display can improve the chromaticity uniformity. It is achievable.
We found that even the same grade of LEDs of the world's first brand has a large wavelength deviation and color saturation deviation, and the deviation range greatly exceeds the threshold value of the human eye for the discrimination of green color difference. Therefore, the color uniformity correction is carried out. It is of great significance.
In the CIE1931 chromaticity diagram, according to the law of the center of gravity, we found that: at any point in the G file range (u0026Square; abcd) mixed with a certain proportion of red and blue, the color coordinates of the mixed color can be adjusted To the intersection O of the straight line cR and the straight line dB.
Although the chromaticity uniformity can be greatly improved. However, the color saturation after correction is significantly reduced. At the same time, another prerequisite for the use of red and blue to correct the uniformity of green chromaticity is that the three types of red, green and blue LEDs in the same pixel should be distributed as closely as possible to make the mixing distance of red, green and blue as close as possible to achieve better results. Effect. At present, the LED uniform distribution method is commonly used in the industry, which will bring confusion to the chromaticity uniformity correction. In addition, how to measure the color coordinates of tens of thousands of red, green and blue LEDs is also an extremely difficult problem. We gave a hint about this.
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