Unified standards for the display industry are necessary
Liu Peizheng, former Secretary General of the LCD Professional Branch of China Optical Optoelectronics Industry Association
Different display technologies such as CRT, LCD, PDP, OLED, LED, etc. all have their own advantages. It is not fair to compare the advantages of different display technologies from one aspect. Therefore, it is necessary to develop relatively uniform and wide-ranging standards for different display technologies. High-definition television requires that the displayed image and the actual image do not differ under human eye observation, so various technical indicators of the display device, such as resolution, contrast, grayscale, response speed, color reproduction degree, brightness, etc., should be formulated. A series of indicators to ensure that people see the same TV image as the actual image. At present, LCD, plasma, projection, LED (light-emitting diode) large screen and CRT (CRT) can make satisfactory video products, can make high-definition products, but the work of developing uniform standards is still very important. .
CRT TV dominates CRT, LCD (liquid crystal), PDP (plasma), OLED (organic light-emitting diode), LED, projection display and other display technologies, each with its own advantages and disadvantages. It should be said that there is no best display technology in the world, only the most suitable display technology under certain application conditions. Therefore, each display technology should develop a new application market according to its own characteristics, rather than substituting others' products. At present, the most products based on LCD technology have become the mainstream products of the display industry. The development of LCDs has made portable displays possible and has driven the development of mobile phones, notebook computers, desktop computers and other industries. Since the invention of CRT technology in 1898 to 100 years in 1998, CRT technology has always been in the dominance of the display industry. Until 1998, full-color PDP, LCD and LED large screens gradually developed, and the developed countries of the world began to vigorously promote the digital TV industry, and the CRT industry really began to decline. However, in the current world of analog TV, the performance and cost performance of CRT TV is still the best. The 25-inch to 34-inch CRT TVs still have a market size of nearly 100 million units worldwide. The performance indicators of PDP technology are now comparable to CRTs, making it the best choice for home theater viewing. However, due to the low brightness and high power consumption of PDP products in the past few years, LCD TVs have gained a head start. Currently, there is no substantial difference between LCD TVs and PDP TVs. Consumers who prefer to watch TV and watch large movies in darker lighting conditions may choose PDP TVs, while consumers who prefer brighter lighting environments will choose LCD TVs. 10 years ago, because the PDP working voltage needs hundreds of volts, the power consumption is large, and the LCD also has problems such as long response time, unsatisfactory color, and poor viewing angle. Therefore, some people are optimistic about the OLED display and believe that it is the only third-generation display device that can replace the CRT. However, from the current point of view, OLEDs have advantages in color display products below 10 inches, and can compete with LCD displays between 10 inches and 32 inches, but above 32 inches, various performance indicators of OLEDs are similar to PDPs. Whether it has competed for PDP and LCD, it is currently a question mark. The biggest advantage of projection TV is the portable large-screen display, which is the best choice for education, business activities and mobile movie screening. Due to the high brightness of the LED array and the harsh environment, the LED large screen is the best choice for outdoor advertising, sports, stations and other applications.
Experts in different display devices have advantages and disadvantages. Experts in display devices should be careful that one product is better than another. If you want to talk about it, you should have scientific and rigorous data. The environmental conditions for comparing the two devices should be clear. In addition, the comparison cannot be based on the level of indicators, but should be based on the actual needs of people, based on the standards given by the state or industry. Now some media and experts believe that PDP TV is better than LCD TV, and OLED TV can replace LCD TV. This argument is unscientific. It can only be said that some places in PDP are better than LCDs, and some places in OLEDs are better than LCDs. The performances of various display devices such as CRT, PDP, OLED, SED, FCD, etc., such as viewing angle, response speed, color, etc. are actually similar. The final win depends on who has high luminous efficiency, who is mature in production process, and whose cost performance is low. However, when some people compare these three indicators with LCD, they rarely see the difference in performance between them. Their common problem lies in the use of high current drive technology, the fabrication of integrated circuits is difficult and the cost of fabrication is high, and the line loss is much larger than that of LCD products driven by TFT (thin film transistor) voltage. Recently, some media have strongly promoted that LCD TVs have far less dynamic resolution than PDPs, and there are tailings during dynamic display, poor color reproduction, high brightness, and glare. However, according to recent customer visits to the three major electronics stores in Dazhong, Gome and Suning, most people can't distinguish between LCD and PDP TVs (playing the same image) before the Panasonic booth. When the LCD TV plays football, basketball, or when the player runs and scores, the consumer can't see the motion picture with or without tailing.
Uniform standards should be developed The biggest problem facing HD digital TV is still the issue of standards development. Whether the factory specifications of the high-definition LCD TVs and PDP TVs produced now meet the standard specifications are a concern. Of course, the higher the indicator, the better. High indicators are often associated with high costs, and most consumers are looking for the most cost-effective products. For these products, we also need to study the characteristics of the human eye observation image at the same time, such as the resolution of most people on the graphics, and some people think that the line resolution is 10 lines / mm, the angular resolution is 0.1 degrees. In addition, the resolution is related to the distance of viewing and the brightness of the environment. The image requires that the pixel size of the liquid crystal display device is related to the distance of the observed image. For example, the viewing distance of the mobile phone and various handheld displays is close, so the pixel size is generally between 0.1mm-0.2mm, the notebook computer is generally between 0.2mm-0.25mm, and the desktop computer is generally between 0.25mm-0.33mm. LCD TVs are generally between 0.5mm and 0.7mm, which is the resolution requirement of static resolution. An object is more static when viewed from static, so dynamic resolution is less demanding than static resolution. The response time of a typical CRT and PDP TV is at the level of 1ms-2ms, while the response time of an LCD TV is at the level of 4ms-8ms. In fact, all display devices have a trailing tail, but the length of the trailing tail is different. LCD TVs with tens of milliseconds of response time in the past can indeed see table tennis and football have a tailing phenomenon during sports. Now the response time of LCD TVs can generally be less than 10ms. LCD TVs are rarely seen during the Beijing Olympics. There is a tailing phenomenon. At present, the LCD TV has not seen the process of changing the ball from a circle to an ellipse when playing soccer or basketball. In addition, the current resolution is represented by 720 lines and 1080 lines. The detection method is tested with black and white lines with the largest contrast between black and white, but the actual TV is color. Can the black and white line be good or bad? Bad, it is still difficult to determine, the resolution can not tell the quality of the TV. In addition, how to evaluate the color of a TV set? Everyone may think that the color reproduction of liquid crystal is not good, it is not as good as plasma, LED and laser TV. In fact, the purity and consistency of the three primary colors on the LCD screen is much higher than the plasma. The LCD dyes three colors on a glass substrate, and the color purity, color consistency, and reliability can be well done. Using CCFL (Cold Cathode Fluorescent Lamp) as a backlight is cheap, but the color performance is not very eye-catching. If the same LCD screen uses LED as the backlight (ie LED TV), its color can be compared with PDP TV. If a laser with a better color purity is used as the backlight of the LCD screen (ie, laser TV), its color can be superior to that of the PDP TV. So it's not that LCD TVs are not as good as PDP TVs, but whether consumers need high-definition TVs. For the average consumer, the color of the CCFL backlight LCD TV has been very bright. Some experts think that when the color reproduction degree of TV reaches 85%, the difference in color between the displayed object and the original object will not be seen by the average person. If it reaches 90%, it cannot be distinguished. Therefore, it is necessary to develop uniform standards for different display devices.
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