Cinemas, a new application field for LED displays

LED displays have to comply with DCI standards if they are used for movie theaters. The DCI organization was jointly created by the world's six largest film companies to establish a unified digital movie playback standard, and to protect the copyright of digital movies and ensure the audio-visual experience of theaters. The DCI standard covers data formats, codec interfaces, transmission methods, security, and theater hardware systems including servers, projection, audio, and control.

It is true that the LED display control system can reduce the LED display with high design brightness to 48 nits through gray scale control, but it will bring many low gray display problems, such as red color floating, pixel unevenness and so on.

Limited by the minimum current specification of the drive chip, the drive current of the LED cannot be reduced indefinitely. This requires the LED to reduce the luminous brightness through its own design, such as further reducing the chip size or entering more into the package. Light-absorbing particles. However, this is all at the expense of photoelectric efficiency. If the minimum drive current of the drive chip can be further reduced, or the number of supported scans can be further increased, the brightness of the LED display can be reduced without sacrificing the photoelectric efficiency. For the LED itself, only the R, G, and B chip ratios that are suitable for the color ratio of the DCI white balance point are accurately selected, and the brightness that can meet the current requirements of the driving chip in the future, is the most perfect LED that meets the application requirements.

LED color requirements

According to the DCI-P3 color gamut defined by DCI, the R, G, and B primary colors of the display have strict color coordinate requirements. For LED displays, strict color coordinate specifications are required for LEDs. However, currently on the market, most LED suppliers use dominant wavelength specifications to define colors, and dominant wavelengths are colors defined from one dimension (hue), missing another dimension (saturation) of color information. The color of the same dominant wavelength corresponds to a straight line passing through the iso-energy point (0.333, 0.333) in the color space, rather than a precise color point. Therefore, in order to accurately meet the requirements of the DCI-P3 color gamut, it is first necessary to select an LED whose color coordinates define the color, rather than an inaccurate definition of the dominant wavelength.

Due to the principle of display light mixing, the initial design color gamut of the display screen can be equal to or greater than the DCI-P3 color gamut, that is, the initial design color coordinates of the three primary colors of R, G, and B need not be directly the color coordinates specified by DCI-P3. It is the area formed by the bilateral extension line of each base point and the color space boundary as shown in the figure (as shown in Figure 2). Among them, green and blue are respectively a small area similar to a triangle. Due to the color dispersion of LEDs, such a small color range is almost impossible to achieve in mass production of LEDs; for red, the basis point specified by DCI-P3 has been Located on the boundary of the color space (saturation 100%), so in theory, LED has no possibility of satisfaction.