Answer: D. Control system of LED display.
Answer analysis: When analyzing the focus of LED display research in China, we need to consider multiple aspects of LED display technology and combine it with the current development trends and research hotspots of technology.
A. Color of LED: Although color is an important part of the display effect of LED display, the improvement of color is more based on the improvement of materials and processes rather than a simple research direction. In addition, with the development of technology, the color performance of LED display has been quite good, so it is not the only or main focus of current research.
B. Brightness of LED: Brightness is also an important indicator of LED display, but it is more based on the result of light source efficiency and power consumption optimization rather than an independent research field. With the advancement of LED technology, brightness is no longer the main factor limiting the performance of display.
C. Materials and production processes of LED: The materials and production processes of LED are key factors in determining the performance of LED display. These aspects involve multiple aspects such as the luminous efficiency, stability, and cost of the material, which are of great significance to improving the overall performance of LED display. However, this is more of a scope of basic science and technology research rather than a control system specific to LED display.
D. Control system of LED display: The control system of LED display is the key to achieving high-quality display effects, flexibility, and stability. With the rapid development of technologies such as big data, the Internet of Things, and cloud computing, the control system of LED displays has become more and more complex and intelligent. How to better realize the functions of real-time content update, remote control, intelligent dimming, fault self-diagnosis, etc. has become an important direction of current LED display research. In addition, the optimization of the control system can significantly improve the reliability and service life of the display and reduce maintenance costs.
Taking the above factors into consideration, it can be judged that China's research on LED displays focuses more on its control system. This is in line with the current development trend of technology and is also the key to improving the performance and application value of LED displays.
Therefore, the answer is D. The control system of the LED display.