This year, LED full-color screen large market demand for a rapid increase in the momentum of the Chinese New Year has just passed, the project began bidding. Si Wuyue copies, although the impact from SARS, but only so that the postponement of the implementation plan, rather than the item was withdrawn. After SARS, the formation of many to step up the implementation of the project. Major large LED screen manufacturers and the amount of the contract compared to the same period last year, up 20%, some even more than last year almost doubled. There are many new entrants into the full-color screen large areas of the company's success is also very good. As in previous years compared to the market this year, germinating early and large number of projects have been implemented by tens of millions of dollars more than a dozen projects there. Into the third quarter, a number of major projects into the bidding stage. Another feature is that business investment by a marked increase in projects, which include commercial advertising in the application. It can be said that, LED large screen as a commercial advertising media, in silence for nearly 10 years later, again by the advertising industry's favor. At the same time, full-color screen is also encouraging export situation. Early in September, held in Shenzhen, the annual Light Fair, the exhibition, over the past year is the industry's largest LED display. Large LED screen, LED lighting, LED traffic lights, LED production equipment, testing equipment, such as silver, that China's LED industry has come a new upsurge. I believe that this exhibition is a sign to mark the LED industry in China reached a turning point in the home-made. Internationally renowned LED LED manufacturers, screen manufacturers have begun on a large scale to the mainland of China, the mainland of China will be the LED products and its manufacturing center. Broad market and good investment environment, low labor costs, making China the world's electronics industry is becoming the manufacturing center. As computers, mobile phones, television sets, electronic products, China is also a large LED screen manufacturing industry.
As has long been engaged in large LED screen R & D scientists and technicians, I have been concerned about China's large LED screen development, large-screen display of international concern about the new achievements in the industry. Three years ago, in the author "LED large screen of development" in an article, when it comes to China's largest LED screen in several applications and features, and large full-color screen is the image of our country in the works. It should be said that this did not change the overall pattern, but the increased demand for commercial advertising is also very important in the near future. It can be said that our large full-color LED screen industry is ushering in a new climax. A serious look at the market development and technological progress of the new situation, the right to take measures to seize the opportunity to enhance the rapid and sustainable development, should be worth studying counterparts. Here take the liberty of the relevant technical issues, and experts hope that the peer correction.
Image 1: targeting world-class level
The image of the project refers to the construction of large-screen is the main purpose of a city or a major activity to add style, it does not create a direct economic benefit, but to raise awareness of the city, the creation of a city's image and improve the investment environment, create a business atmosphere conducive to economic The development of good social benefits, and thus indirectly to create economic benefits. The image of government investment projects mainly focus on social benefits, or not is not the main business operations through cost-effective. In recent years, many parts of the country in the construction of large urban centers or the public square of Plaza Leisure large LED screen, is a typical image of the project. A lot of stadiums LED display, the stadium is necessary for the modernization of facilities, is also in this category.
Is the image of the project, as far as possible the inevitable pursuit of a perfect performance and effectiveness, especially in high-quality video images. Tongsudeshuo is to make color television giant, which is a number of domestic manufacturers has been working for a long time, but also made considerable progress, but falls short of the ideal goal of the far, and foreign large full-color Screen, the gap is still very great.
Earlier this year, Hunan, Nanjing Road Commercial Street, voted heavily in the construction of an area of 114 square meters of large full-color screen, the screen UNITEK by the British construction company, has been running for more than six months from the effects of view, can be present Domestic best big screen. I participated in the screen design and technical specifications of the final acceptance testing, there are many aspects of domestic and follow the example of peer learning.
As a large full-color screen, the key technical indicators are: high enough brightness, viewing angle and distance; a good time to restore the color; high enough capacity to gray; high enough to scan refresh rate. High enough video signal processing capability, in particular, consistency is better, the structure of the process, also have great skills. Hunan Road when the big screen in the tender set by the technical indicators are:
White light is greater than 5000cd/m2;
White Balance color temperature 6500K;
Video processing is greater than the median 10bit;
Gray-scale for each color is greater than 10bit, to 1.07 billion color display;
Refresh rate greater than 400Hz;
It can not be aware of the color display, full-screen color the color difference is less than 4nm;
It can not be aware of the screen brightness difference, adjacent pixel brightness difference is less than 5%, showing red, green, blue gray monochrome screen, there was no noticeable phenomenon mosaic;
MTBF is greater than 5000 hours, MTTR less than 30 minutes;
Objectively speaking, these indicators, not only at the time, that is, today, domestic manufacturers of the product has not been fully achieved. In many cases, due to the LED level, the normal design of large-screen brightness has been no problem, be able to meet the requirement. However, the brightness is an important indicator, but not all. It is now generally felt that domestic manufacturers of large-screen brightness more than enough soft, the overall effect of less well-known foreign manufacturers, because the more technical issues yet to resolve. The author believes that from a technical point of view, it is necessary to make efforts in the following aspects.
(1) and color blending
Large-screen by a large number of LED components, must be used by light-emitting diode optical parameters of the design, calculation and testing in order to achieve a good white balance. Simple estimates by the naked eye and feel it is impossible to judge a good effect. Here involves the selection of light-emitting diodes and design-driven, not only affects the optical properties of the screen, but also affect the reliability. Especially in the full-color interior design, thermal design should be given sufficient attention, otherwise the effectiveness and reliability will be a problem.
(2) color correction
Due to differences in color coordinates, television video signals with LED color gamut of differences, resulting in the broadcast TV color appears to be untrue. Therefore, the color coordinates of the correction is very important. Correction conversion calculation more complicated and difficult to use software from various manufacturers of the product, even though we all claim to have such a color correction features, I am afraid, do not do color correction.
(3) Consistency
Large full-color screen is the most difficult consistency, or the audience most likely to be aware of the problems is that consistency is not good, a screen appears to be a shallow depth, commonly known as Mosaic, is the most offensive. Caused by poor consistency are many reasons, including the selection of light-emitting diode, drive circuit, structural design and construction, and so on. However, unless the light-emitting diodes used too discrete, otherwise the consistency of the problem is that the design and construction problems. Hunan Road big screen, the audience is reflected in the first observation of the phenomenon of less than Mosaic (Strictly speaking, it is not light, the general audience and professionals to observe a number of differences). This big screen in the very structure of the process on the characteristics, there is no domestic use of commonly used methods such as plastic irrigation module, which is worth studying. Typically, LED manufacturers according to the brightness of the light-emitting diodes and color products is divided into several files, the file of the same differences can be resolved through careful design and debug solution. Structural design and construction of non-performing, the mosaic is another big reason for the phenomenon, often to the big screen installed and put into operation only when it is found that no remedy, so special efforts should be. If domestic manufacturers of electrical indicators on the screen in a certain gap, then the structure and process on a much larger gap, which is often seriously affected the results show.
(4) gray level
Hunan Road and abroad, many big-screen big-screen experience has shown that the gray level must be high enough. At present, high-end products for the general-screen display with 1024, 1.07 billion colors. 256 are domestic, far. Many manufacturers even 1024/2048/4096 to 16,384 coding, 256 non-linear color display 16.7 trillion. The view was expressed that 256 non-linear gray-scale for the large screen should be enough, because the HDTV standard also provides 256 gray. As far as I tested, this is not the case, the actual results varied widely. As a matter of fact to achieve more than 1024 gray, will increase the technical difficulty of many. A simple calculation will understand. As for 400Hz refresh rate, non-linear gray-scale for 1024, to adjust the brightness level to 32, then if the correction factor for the Center 2.8, PCM minimum width of the pulse width of 10ns or so should have been driven to achieve Circuit bandwidth limit. That it is impossible to achieve, it is necessary to consider the AM and the use of composite width. Similarly, there are transmission bandwidth, when the ranks of several multi-screen, high refresh rate (for example, more than 400Hz), data transmission will be difficult, and sometimes must use optical transmission in order to guarantee the quality of the image. Therefore, non-linear gray from 256 to the non-linear 1024, a leap in technology.
(5) digital processing power
To get high-quality images, there must be a high-quality video signal source. For the average large-screen users can get the best signal that is broadcast TV signal, DVD, VCD, and so is the domestic level. Therefore, the input signal for digital processing to enhance image quality is essential. As a matter of fact we have such an experience: players selected programs, the results show that it is very satisfactory, but if it is live TV show or VCD / DVD, it is inevitable that a variety of screen and the camera, for example, the night scene or dark screen A large area of high-brightness bright screen, then the effect will be greatly reduced. How can a variety of images in the camera and under are satisfied with the effect? Which rely on digital signal processing, such as digital comb filter, filter noise reduction, sharpening edge, predict and remote compensation, as amended color, non-line Of the amendment, and so on. Of particular note is the zoom ratio (SCALE) to deal with, is the largest LED screen in a special issue of up to the big screen industry research efforts. As the big video screen pixel is always less than the source of information in the broadcast when the inevitable problems encountered in scaling, sampling and in return, as well as the loss caused by aliasing and image quality can cause Defects decline. How to reduce damage and reduce the need for digital signal processing technology. Digital image processing technology has made great progress, there are many results, such as large-size TV or projector in the technology can be directly applied to large-screen display in the past. Digital processing capacity of the system embodied in the median processing and processing speed, the use of high-end FPGA or DSP is an inevitable trend.
(6) and the reliability of life
Reliability is a display of life, whether it is used to project the image of, or used for commercial operation, stability and reliability are crucial. The reliability of indicators by the MTBF (MTBF) and mean time to repair (MTTR) to express. MTBF10000 hours is a very high indicator, in fact does not necessarily need. Many manufacturers have made great efforts to improve the reliability of the system, but how to achieve what level does not provide convincing data. At present, the domestic has not been on the big screen the reliability of the test. Reliability is based on the rigorous design and the reliability of strict quality control management. Display is a large-scale electronic devices, to ensure that there is a good day-to-day maintenance and periodic maintenance of conditions, can be targets for lower MTBF and save money. The reason is simple, if we do not require large screen for a long run, but intermittent work, and in the interim period, through the maintenance, the failure to eradicate signs, so that the system has always been in good condition, then, we can not guarantee the normal work period Failure. In this way, 1,000 hours of MTBF can also stable and reliable system to function. Hunan Road big screen, the opening has been running for eight months, the major indexes did not decline significantly. Not only because of higher system reliability, but also because of better maintenance. More prominent, large-screen design of the structure and well equipped with spare parts, MTTR can be achieved within 15 minutes, which we should follow the example of the special.
2 commercials: the best efforts of the cost
The most eye-catching and it is encouraging that for commercial advertising, such as the large full-color screen is the rise of a new wave, which is not only economic development but also technological progress. The author believes that this upsurge in front of the right to take business strategy and technology strategy is to ensure that the key to sustainable development. First of all, users and audience response to the necessary guidance to ensure sustainable development and a higher level.
From a technical point of view, I believe that the pursuit of the screen is not the best, but the pursuit of the best cost performance. Text, animation and treated the main screen image, not to focus on video, and even does not require real-time broadcast television programs.
Commercial operation is about economic efficiency, as advertising media, it is necessary to be able to attract the attention of the audience, advertisers have been approved. In a word, must be a big-screen manufacturers, advertising, and advertisers will benefit from it. In a variety of advertising media, big screen has the advantage of its rapid change, with colorful; disadvantage is that large investment, high cost and high cost. How to reduce costs, lower cost, in recent years, there are many good ways on the technical specifications here would like to put forward my views on the issue.
(1): The purpose of advertising is to promote and attract eyeballs to establish a deep impression on the audience, beautiful screen is important, but it is not only a video or television program is the best. Through a variety of creative means, such as changes may also serve the same good results. The lights change very limited, and so on several patterns changing, the effects are not bad. Big-screen performance in the form of neon lights more than enough advertising purposes. That there must be full-color video effects, big screen to show the idea of one-sided. In fact, in the United States, the largest video screen is not more concentrated in certain areas, such as the New York Times Square, Las Vegas and so on. In order to avoid dispersion driver's attention, the United States law does not allow rapid changes in the ad. Text and graphics with a simple change should be more ad sales. Animation (such as FIASH) may be the best method of performance. In our country, used to the big screen on the screen is divided into synchronous and asynchronous two types of screens. Synchronize the computer screen as the monitor, change, full-function, but inefficient and need to work a computer and communications always running. Asynchronous screen is a single chip or embedded control systems, display the contents of a write until the next update so far. High-end processor to achieve the same gray and video effects, asynchronous screen in many cases more suitable for advertising and information change more slowly, but has not yet accepted for a wide range of users.
Simple or small single-chip embedded systems with low processing power, in the gray-scale display and refresh speed will be lower. However, the performance of text, animation, as well as pictures of a variety of changes, there are still adequate.
(2) brightness: As we all know, direct sunlight in outdoor conditions, the need to 5000nit brightness in indoor 1000nit around enough, there are intermediate between the semi-outdoor, which is the consensus of the industry. I can see a large outdoor screen, if only in the night, the indicator light will be able to significantly decrease the cost of course dropped. In other words, if the big screen, do not work during the day, evening show, as a commercial advertising should be a good idea. In fact, neon is currently the most widely used outdoor advertising media. The neon luminance than the large LED screen is much higher, but it does not require the neon open during the day, then asked why the big-screen work during the day? But also to direct sunlight in the next broadcast video programming can be seen clearly, there is in fact guide the user. Moreover, the audience at night than during the day and much, much more effective it is. Taiwan. The company launched a billboard, the image is fixed during the day, at night is full-color screen activities, the cost is only common outdoor one-third of the full-color screen is a clever strategy.
(3) of the resolution: the resolution or pixel resolution depends on the density, the cost of the display, the pixels account for more than half of the cost. As a result, reduce the cost of pixels is the most attractive, split-pixel technology, or dynamic pixel technology is used. Dynamic pixel technology is not new technology, at least have spent more than 10 years, through the pixels on the composition of the share of the ways in which to raise the visual resolution of a number of times. For example, the most commonly used to share the 2R1G1B can pitch d for the big-screen visual resolution to d / 4 effect, resulting in fewer pixels can display a larger picture. It must be pointed out that the visual resolution of d / 4 dynamic pixel screen is not the same as in d / 4 of the big-screen resolution of Physics, many domestic manufacturers in the promotion of dynamic pixel technology, in some cases is an exaggeration. Pixel technology to achieve dynamic variety of methods, as are the use of the residual principle, it is using the human visual temporary stay, with fewer pixels can display the activities of the larger picture. It must be pointed out, dynamic pixel technology with fewer pixels show a larger picture, because of the impact of aliasing image will be fuzzy, poor clarity, sometimes flashing, and it can not be as good as the pixel.
Last year, Shibuya, Tokyo, Japan, a large-scale commercial buildings, large and small have built a six-storey-story electronic display. The screen mounted on the inside of the glass curtain wall, does not affect the building's appearance and lighting. Play video ads in the evening, through the unit's display space, you can see lights inside the building. Due to avoid outdoor work in harsh conditions, construction costs are much lower. Its great distance between points, using the residue as technology, a number of pixels is only one-fourth of the pixel. Although the results can not be compared with dot-matrix screen, but the Nasdaq in New York than the big screen, and new ideas to save money, it is worth promoting in areas where conditions permit.
It is worth mentioning that Shenzhen-day-hui's full-color color is not used to reduce the pixel approach, but to reduce the high price of pure green tube Chunlan way through the clever structure of the arrangement was very good The effect of color, the higher cost, full-color screen in favor of universal application. This theory is based on the brightness of the human eye for the resolution of high-power, and the colors for the low-resolution, color television is the use of this principle to reduce the bandwidth. However, we all know, in the three primary colors to achieve white balance, the largest contribution to the green, green tube to reduce Thus, it is bound to affect the brightness of the screen, so this method does not apply to high brightness of the occasion.
(4) and the reliability of life: reliability, as has already been discussed here to talk about life issues. Life is the system not to return to the technical indicators, and the reliability of it, but it is not the same concept. The big-screen life depends largely on the LED life. LED refers to the life of the LED light intensity dropped to half of the nominal value. Long-life LED, as the electronic devices in military supplies, the price is much higher. LED light tubes with the decay of the quality of the work of the current working environment and a great relationship, even the famous Long Life, if the state does not work properly, will shorten the life span of these costs are related. Almost all manufacturers have LED life as a big-screen life is actually wrong. Big-screen life of what should be the number, but also a cost issue. Calculation of business operations and return on the investment screen, the best ratio. In most cases, require 100,000 hours of life is not only unrealistic and unnecessary.
(5) the rest of the technical indicators, such as the gray-scale, the refresh rate and dynamic range, such as: data bandwidth used for commercial advertising screens, should cost from the perspective of choice here, not more. It was divided into the big-screen broadcast quality, professional-level, multi-media class, and class summary of the four-level, functional and video effects, it is more scientific. It should be based on the practical application of the requirements and the level of investment to select the most appropriate use of the big screen. Selection of project the image of broadcast quality and professional-class, business-class multi-media advertising to focus a simple graphical text can be simple level. As the big screen often, they should tender landlords in the tender should be determined before the construction of what kind of big-screen, in a practical on the basis of competition. Some manufacturers put forward unrealistic targets, indicators and mislead the owners to bid up the suspects. Manufacturers to science, faith the attitudes and operating style of the owners to treat, treatment products, is the real development. I believe our industry will show a healthy sustainable development, we are confident of our future.
Reference link: http://www.17led.com/LEDdisplay/2008-04/61.html
