LED display color of all kinds of processing technology

Time:2018-11-29 Views:157

LED display chroma processing technology from the most basic color wavelength selection, white field to the deployment of color temperature, to improve the color reduction degree of color space transform to treatment and to improve the quality of chroma uniformity processing, and then to today in order to expand color gamut reappear more nature and take more colors (more than three colors) disposal, all sorts of color processing technology throughout the history of the LED display, in the LED display the comprehensive discipline one of the most core technology.

Analysis of various chromaticity processing technologies of LED display screen:

1. Selection of primary color wavelength

LED display has a very wide application in all walks of life, and applications in different places have different requirements for LED gezer wavelength, LED gezer wavelength selection for some of them are in order to achieve good visual effects, some of them are in order to meet people habit, and some is the industry standard, national standard, and even the international norms.For example, the selection of primary color wavelength of green tube in full-color LED display screen;In the early stage, yellow and green LED with a wavelength of 570nm was generally used. Although the interest rate was low, the color range of the display screen was small, the color reduction degree was poor, and the brightness was low.After the pure green tube with a wavelength of 525nm was selected, the color range of the display screen nearly doubled, and the color reduction degree was greatly improved, greatly improving the visual effect of the display screen.For example, on the stock price display screen, people usually use red to indicate the rise of stock price, green to indicate the decline of stock price, and yellow to indicate the flat price.In the transportation industry, the national standard strictly stipulates that the blue and green bands are passable and the red bands are prohibited.Therefore, the choice of primary color wavelength is one of the important links of LED display screen.

2. Coordinate the deployment of white field color

The coordination of white field color coordinate is one of the most basic technologies of full-color LED display screen.However, in the mid-1990s, due to the lack of industry norms and basic test means, the coordinate of white field color is usually determined only by human eyes and perception, resulting in severe color bias and arbitrate of white field color temperature.With the publication of industry regulations and the completion of testing methods, many manufacturers began to standardize the color matching process of full-color screen.However, due to the lack of theoretical guidance of color matching, some local manufacturers often sacrifice the gray level of some base colors to allocate the 100-field color coordinate, and the comprehensive performance cannot be improved.

3. Chroma uniformity treatment

Color uniformity of LED display screen has always been a major problem troubling the industry. It is generally believed that the uneven brightness of LED can be corrected by a single point to improve the brightness uniformity.However, the color uniformity cannot be corrected, which can only be improved by subdividing and screening LED color coordinates.

As people more and more high to the requirement of LED display, only to the LED color coordinates are subdivided and filter have been unable to satisfy people captious eye, comprehensive correction disposal of display, the chroma uniformity is improved which can realize the discovery of even the first international brand with a LED also exist in the larger wavelength deviation and deviation, color saturation and the range of the deviation greatly exceeds the threshold value of the human eye to the green color identification, therefore, it is significant to chroma uniformity correction CIE1931 chromaticity diagram, according to the laws of gravity center, found that G gear range (& Square;Any point in abcd where green is mixed with a certain proportion of red and blue can adjust the color coordinate of the mixed color to the intersection point O of line cR and line dB.

Although can make chroma uniformity improves greatly.However, after correction, the color saturation decreased significantly.At the same time, another premise of using red and blue to correct the uniformity of green chromaticity is that red, green and blue leds in the same pixel should be distributed as centrally as possible to make the mixing distance between red, green and blue as close as possible, so as to achieve better results.At present, the uniform distribution method of LED commonly used in the industry will bring chaos to the correction of chromaticity uniformity.In addition, how to measure the color coordinates of tens of thousands of red, green and blue leds is also a very difficult problem.I gave you a hint.

4. Color restoration treatment

The birth of pure blue and pure green LED makes the full-color LED screen popular in the industry with its wide color range and high brightness.However, due to the large deviation between the color coordinate of red, green and blue LED and that of the red, green and blue color coordinate of the PA L TV system (see table 1), the color reduction degree of the LED full-color screen is poor.Especially in the expression of human skin color, there is a relatively obvious visual deviation.Therefore, the color restoration disposal technology arises at the historic moment.The author recommends two methods of color restoration:

Firstly, the color coordinate space transformation of red, green and blue three-base LED is carried out to make the three-base color coordinate between LED and PA L TV as close as possible, so as to greatly improve the color reduction degree of LED display screen.However, this method greatly reduces the color range of LED display screen and makes the color saturation of the screen drop sharply.

Second: only the most sensitive color gamut of the human eye is properly corrected;However, the color gamut that is not sensitive to other human eyes should reduce the original color saturation as little as possible.In this way, a balance can be achieved between color reduction and color saturation.

Method for the chromaticity treatment of 53+2 multi-base colors

In recent years, the field of flat panel display is keen to discuss 3+3 multi-base color display (red, green, blue plus yellow, green and purple) to expand the color range and reproduce more abundant natural colors.So, can the LED display achieve 3+3 multi-color display?

It is known that in the visible light range, yellow and green are monochromatic light, and yellow and cyan LED with high saturation have been obtained. Purple is compound color light, while purple LED with single chip does not exist, although I cannot realize the red, green, blue, yellow, green and purple 3+3 multi-color LED display screen.However, it is feasible to study the red, green, blue, yellow and blue 3+2 multi-base LED displays because of the existence of a large number of highly saturated yellow and cyan colors in nature.Therefore, this research is of certain value

In the current various TV specifications, video source only red, green and blue three primary colors, and no yellow, green two colors.So, display terminal yellow, green two primary colors how to drive?In fact, when determining the driving intensity of yellow and blue primary colors;Following the following three principles:

(1) the purpose of adding yellow and blue primary colors is to expand the color range and thus improve the color saturation.But the total brightness value cannot change;

(2) do not change the hue while increasing the color saturation;

(3) centered on D65;Taking the boundary of RYGCB gametrochromatic domain as the endpoint, linear expansion is made for each point in the gametrochromatic domain.

All the above chromaticity processing technologies are related to each other in some aspects, and even the integrated LED display that cannot have both fish and bear PAWS must undergo brightness uniformity correction, gray nonlinear transformation, noise reduction processing, image enhancement processing, dynamic pixel processing, etc. The whole signal processing process is very complex.Therefore, it is necessary to comprehensively balance the performance from the perspective of the system, master the order of each processing, and increase the depth of signal processing, so as to make the LED all-black screen show a colorful, colorful wonderful world.