The Hong Kong Academy of Sciences is a research and development institution established by the Hong Kong Government in 2001. Its position in the local area is comparable to that of some large research institutes in the Mainland. ASTRI's operating model is flexible, R&D is completely "customer-oriented", and it focuses on "creating substantial industrial benefits". It is very significant in terms of quality and industrialization of scientific research results. The operation mode of the institute can be used by domestic research institutions for reference. At the ASTRI Science and Technology Project Promotion Conference last September, the author and the ASTRI experts made in-depth exchanges. The latest dynamic backlight technology of the institute left a deep impression on the author. In order to further understand the situation and their views on technology trends, we interviewed Dr. Cai Zhenrong, Director of Display Systems Department of Hong Kong Applied Science and Technology Research Institute.
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Dr. Cai Zhenrong, Director of Display Systems, Hong Kong Applied Science and Technology Research Institute
High-tech LED: What achievements has ASTRI achieved in dynamic backlighting in the past few years?
Cai Zhenrong: In the past four years, ASTRI has been committed to the research and development of LED backlight technology. At present, it has applied for more than 10 US patents, and some have been authorized. Related articles won the 2008 International Display Conference (IDW) Outstanding Paper Award, and won the China SSL Product Innovation Award for two consecutive sessions in 2006 and 2008. Our main research directions are LED backlight design and dynamic backlight control.
For backlight design, we designed a direct-lit white LED backlight, a direct-lit RGB LED backlight, a multi-block side-lit LED backlight, and a large-size monolithic edge-lit LED backlight. The design covers optical, mechanical, electrical, drive control, thermal management, etc., and even Japanese manufacturers who have always been known for their design appreciate it.
In terms of dynamic backlighting, ASTRI has developed a variety of backlights to match different backlight designs and product requirements. From the control method, it is divided into local dynamic backlight (local dimming) and global dynamic backlight (global dimming). From color control, it is divided into gray level control, RGB color control and gray-RGB-adaptive control.
High-tech LED: From the current point of view, do you think the past research and development route has gone right?
Cai Zhenrong: ASCO's backlight technology has aroused strong interest from domestic and foreign manufacturers. We have signed direct-backlit backlight and dynamic backlight control technology transfer agreements with two domestic LCD TV manufacturers. They are actively making large-scale quantities. Prepare for production.
Looking back, we feel that the direction of research and development is correct. For example, we believe that LEDs of RG phosphors will become the mainstream of TV backlights. For example, we believe that the dynamic backlights of grayscale regions are the most cost-effective and most productive, and these have been The proof is correct.
For the current mainstream LED side backlight technology, ASTRI developed a prototype three years ago, but unfortunately limited by the large-size light guide plate process capability at that time, it failed to help domestic manufacturers seize market opportunities. In the next step, we will further deepen our cooperation with the industry to develop products that are forward-looking and meet customer needs.
High-tech LED: On the technical route, what do you think is the difference between CCFL, white LED and RGBLED technology? Which technology do you think will win in the future?
Cai Zhenrong: The replacement of CCFL by LED is no longer questioned. In the short term, it is not easy to have new backlight technology to challenge LED backlight. The market share of large-size LED backlights has exceeded market expectations for several years.
Regarding the difference and development trend of phosphor white LEDs and RGB LEDs, I believe that white LEDs represented by red-green phosphors (RG-p) or similar products will occupy the main position of the LED backlight market in the next 2-3 years. This is mainly determined by cost and energy consumption. Currently, RGB LED backlights and phosphor white LED backlights still have a 4-5 times price difference.
The drive system of RGB LEDs is also much more complicated than white light. In addition, since the current RGB mixing efficiency is lower than that of white LEDs, the RGB backlight power consumption of the same brightness is much higher than that of the white LED backlight. In terms of environmental protection and cost considerations, RGB naturally shows disadvantages.
Of course, RGB LEDs also have their unique advantages. The first is the wide color gamut. The color gamut of RGB LEDs can reach 105% NTSC (IEC-1931), while white LEDs are 82%~85%, and CCFL is only about 75%. As the cost of RGB LEDs decreases and efficiency increases, RGB LED-backlit TVs will likely have a place in the high-end market.
High-tech LED: ASTRI's research and development tends to be direct-lit backlighting. What is the original intention of this choice, and how do you view the problems they face?
Cai Zhenrong: The original backlight technology was adopted in direct type. In 2009, due to the promotion of South Korea's Samsung, the side backlight became the mainstream of LED TV backlight. This is due to the combination of the huge impact of the side backlight ultra-thin technology and Samsung's successful business model. In the long run, I believe that the LED LCD TV market will be subdivided, and the direct-lit type will occupy the high-end market, and the metering type will occupy the low-end market.
The direct-lit backlight has a high contrast ratio and excellent picture detail. The main size is 47 inches or more, which is in the high-end market. The main problem currently faced is how to further reduce the mixing distance, simplify the system, and reduce costs.
The side backlights occupy the low-end market with the advantage of ultra-thin and low price, and the size covers 26-47 inches. The side backlight technology threshold is relatively low, but there is still much room for improvement in the process of light guide plate processing, heat dissipation, and system integration. Under the trend of low cost and thinning, in the short term, the side backlight will still occupy the main market.
High-tech LED: Dynamic backlight is the main research direction of ASTRI. How is the research and development in this area at home and abroad, and where is the dynamic backlight technology of ASTRI?
Cai Zhenrong: At present, major TV manufacturers at home and abroad claim to have their own dynamic backlight control technology. Japanese and Korean manufacturers, except for Sharp, are mainly based on gray-scale regional dynamic backlights, but the system is more complicated and the cost is higher. Domestic manufacturers are also actively developing, and have waited for the right time to mass production. This part of ASTRI is very honored to participate and has maintained close cooperation with domestic manufacturers.
In comparison, ASTRI's dynamic backlight control technology has excellent performance, low cost, stable and reliable, and has complete independent intellectual property rights. This is the main reason why domestic first-line TV manufacturers choose to cooperate with ASTRI.
Specifically, ASTRI's dynamic backlight has the following characteristics:
1, high performance. Taking the current dynamic backlight control technology of ASTRI as an example, the dynamic contrast of the TV can be increased by more than 20 times, the static contrast is increased by more than 3 times, and the average power consumption of the whole machine is saved by more than 30%. This performance has reached the world's leading level. Not only that, but we also pioneered the introduction of ambient light into the dynamic backlight algorithm, so that the dynamic backlight control parameters can be automatically optimized according to the changes of ambient light to achieve the best display effect and the maximum energy saving effect.
2, low cost. In the past few years, ASTRI has worked hard to reduce the cost of dynamic backlight control modules from over US$50 to US$5 by optimizing algorithms and improving system resource utilization while ensuring performance. . This may also be the world's lowest cost dynamic backlight control module.
3. High compatibility. Different manufacturers may choose different backlight designs, different LCD panels, and different system solutions. In response to this situation, we have developed a dynamic backlight control algorithm with high compatibility and a dynamic backlight control module. No need to change hardware and main program, just change some parameter settings, you can achieve compatibility with different backlight designs, SD and HD panel compatibility and 60Hz/120Hz compatibility.
High-tech LED: Just now you analyzed the characteristics of various technologies. At present, in the global market, what are the technical characteristics of well-known manufacturers such as Panasonic, Sharp, and Samsung?
Cai Zhenrong: In the field of side backlights, there is no doubt that Samsung is the leader. At present, Samsung's sidelights account for nearly 90% of the LED TV market. However, due to the low threshold of side backlight technology, LG, Sony and domestic Hisense, Skyworth, Konka, etc. have gradually caught up and established independent research and development production capacity.
In terms of direct backlighting and dynamic backlighting, Sharp and Samsung respectively represented two different backlight and dynamic backlight control design concepts in Japan and South Korea. Sharp is taking a high-end route, using thousands of RGB LEDs to independently control the backlight, combined with RGB color dynamic backlight control. This approach maximizes the benefits of LED backlighting and dynamic backlight control, but its high cost is unaffordable for the average consumer.
Samsung and Sharp are taking the opposite technical route, choosing white LED and grayscale dynamic backlight control, and the number of control areas is relatively small. Although the performance in terms of color, contrast, etc. is not as good as Sharp, it has an unparalleled cost advantage, and the price of the TV is more easily accepted by the market.
In general, Sharp's technology represents the long-term direction of LED backlighting, while Samsung's technology represents the most mass-produced solution.
High-tech LED: Faced with the competition situation at home and abroad, different manufacturers have adopted different strategies. Next, where will the research and development direction of the Academy of Sciences go, why are these directions optimistic?
Cai Zhenrong: ASTRI will deepen cooperation with domestic color TV companies, LCD module factories, LED chips and packaging factories, and hope that with the technology and intellectual property accumulated by ASTRI in the past few years, from the perspective of domestic industrial chain integration and domestic manufacturers Accelerate the pace of independent industrialization of LED backlights.
At present, ASTRI is conducting research and development of the next step:
1. Combining image enhancement and image compensation with multiplier and quadruple frequency (240HZ) LED dynamic backlight technology;
2. Thin down direct backlight with regional dynamic backlight control;
3. Large-size side backlight optimization technology;
4. Wide color gamut (NTSC) phosphor white LED and wide divergence angle LED package;
5. LCD electronic digital signage backlight: (a). Double-sided thin LCD display module (15mm) backlight; (b). High brightness (>1500 nits) outdoor LCD display module backlight.
High-tech LED: At present, the LED backlight industry is developing at a high speed. The relevant domestic players are facing huge opportunities and challenges. How do you view the status quo of the domestic industry? What suggestions do you have before ending this interview?
Cai Zhenrong: In the next 3-5 years, LEDs for the large-size backlight market will account for half of the overall LED industry, with LCD LED backlights accounting for the largest market share.
At present, domestic LED manufacturers are limited by product performance and quality, mass production economy scale and vertical integration of industry chain, so the share in this part is still very small, so government units, domestic LED manufacturers and corresponding industry chains should The market is investing more effort.
From a technical point of view, the LEDs used in large-size LED backlights are generally small and medium-power LED chips. Compared with high-power LED chips, the domestic LED manufacturers' ability in small and medium-sized power LED chips is not much different from that of foreign manufacturers. Therefore, I believe that domestic LED manufacturers should have the ability and opportunity to integrate horizontally in the short-term, establish mass production economies and improve product performance and quality.
China is the main manufacturing base and sales market for global color TVs. Therefore, it has excellent opportunities and advantages to further vertically integrate and establish a large-scale backlight independent industrial chain.
Our reporter: Zeng Cong Zeng Aijun
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