Gamut Correction Of LED Display Screen

Gamut Correction Of LED Display Screen

Nov 16, 2017

  At present, LED screen brightness correction and color correction technology can better solve the uniformity problem of the LED screen, and the color gamut correction requires not only the LED screen display image color uniformity, color coordinates of each color more requirements can be accurately fixed in the target color coordinate corresponding to the position, can accurate and vivid colors to display image. The XYZ three stimulus values in this paper are provided by the measurement equipment using CIE1931XYZ color system, and the measurement accuracy is brightness + 2% CIE1931XYZ + 0.0015.


  Target gamut of LED display

 LED display color gamut of pixels, can be regarded as red, green, blue LED color coordinates of the triangle. Because of each primary color LED.The color coordinates are discrete, and each display pixel has different color gamut range. To determine the color gamut of a LED display pixel, you only need to connect the color coordinates of the 3 primary colors when the LED display pixel displays the color. 

 The position of the 3 primary color coordinates of the target gamut of the whole LED display must be within the common color gamut of each display pixel on the LED screen. As shown in Figure 1, two and P2 (P1 LED display pixel color coordinates color coordinate is not true, here only for illustration) due to different color LED color coordinates, the two display color gamut pixels are different, the maximum of 3 color color gamut coordinates together surrounded by color P1 and P2 can display the respectively. When the whole LED screen is displayed on the image, the gamut of P1 and P2 is consistent, obviously showing better display effect. 

  In Fig. 1, the cross section of the two color gamut triangles is a common gamut range, which is probably a polygon shape. The color gamut of LED must be a triangle color gamut when the color is corrected by gamut correction, which is determined by the trichromatic mixture theory used by the display device. The selection of the 3 vertices of the target color gamut will directly determine the display color gamut of the display screen. There are usually two strategies for choosing the 3 vertices of the gamut: (1) the principle of maximizing the gamut, even if the area of the target color triangle is the largest; (2) the principle of standardization, even if the color gamut of the display is close to a standard color gamut, such as xvYCC color gamut. The first strategy ensures the gamut of LED displays as wide as possible, while the second strategy focuses on the fidelity of color and the standardization of product quality. 

  In this paper, a strategy is used to illustrate that the selection of color gamut vertices makes the color gamut area of the target largest. The triangle in the range of common color gamut in Figure 1 is the target gamut of P1 and P2 for application strategy 1. The target gamut is represented by the data shown in table 1.




   The color coordinates and color gamut of the 9 LED displayed pixels in Table 1 are shown in figure 2. The calculation of the common color gamut of these display pixels, such as formula (4):


  As shown in Figure 2 the color gamut in the public as much as possible in the target color gamut, major premise, target selection for RGB color coordinates: (0.687, 0.3105), (0.16, 0.69), (0.138, 0.08). The 3 coordinates are connected together to form a corrected target gamut.