Who knows the history and principle of TV, the more detailed the better!

Television uses electricity to transmit moving visual images instantly. Similar to movies, TV uses the visual residual effect of human eyes to gradually change the still image frame by frame to form a visually moving image. The transmitter of the TV system converts every tiny part of the scene into electrical signals according to the brightness and chromaticity, and then transmits them in turn. At the receiving end, the brightness and chromaticity of each tiny part are displayed according to the corresponding geometric position to reproduce the whole original image.

[Edit this paragraph] Working principle

The sequential sampling, transmission and reproduction of TV signals from point to surface are completed by scanning. Television scanning systems vary from country to country. In China, there are 25 frames per second with 625 lines per frame. Each line is scanned from left to right, and each frame is divided into odd lines and even lines from top to bottom according to interlacing, so as to reduce flicker. Image information is transmitted during scanning. When the scanning electron beam returns to the line retrace line before the start of the next line from the end of the previous line, and the field retrace line after each field is scanned from top to bottom, it should be blanked. During the blanking period of the line field, the line field synchronization signal is transmitted to synchronize the received and transmitted scanning, thus accurately reproducing the original image.

The TV camera focuses the light image of the scene on the photosensitive (or light guide) target surface of the camera tube, and the photoelectronic excitation of each point on the target surface or the change of light guide changes with the brightness of each point of the light image. When the electron beam is used to scan the target surface, an electrical signal will be generated, and its amplitude is directly proportional to the brightness of the scene light image at each point. The scanning electron beam transmitted to the TV receiver makes the picture tube screen change with the strength of the input signal. When scanning synchronously with the sender, the original image will appear on the screen of the picture tube.

The process of TV signal transmission and distribution, taking the live broadcast in other cities as an example, is generally from cameras, TV centers or vans, to microwave relay lines and transmitting stations, and finally to the user's TV receiver. In addition, TV broadcasting satellite and cable TV are also effective means of TV transmission and distribution in national and urban areas respectively.

television band

The scanning system of TV signals in different countries is not exactly the same as the channel bandwidth, so according to international radio consultative committee's suggestion, Latin letters are used to distinguish them. For example, M stands for 30 frames per second, with 525 lines per frame, and the video bandwidth is 4.2 MHz. The total high-frequency bandwidth plus the residual lower sideband of FM sound and AM video is 6 MHz, and K stands for 25 frames per second, with 625 lines per frame, 6 MHz video bandwidth and 8 MHz high-frequency bandwidth. The full TV signal and sound signal of video baseband are modulated to VHF or UHF band respectively for broadcast transmission.

Internationally, VHF has I and III bands, and UHF has IV and V bands. A TV channel is the nominal channel position occupied by a certain TV broadcasting frequency. Different countries adopt different TV standards and channel division is different. In China, the frequency band I is 48.5 ~ 92 MHz, which is divided into1~ 5; Ⅲ band 167 ~ 233 MHz, divided into 6 ~ 12 channels (table 1). Ⅳ band 470 ~ 566 MHz, divided into 13 ~ 24 channels; ⅴ band 606 ~ 958 MHz, divided into 25 ~ 68 channels. The frequency interval occupied by each channel is fixed. The standard of China 625 lines and 25 frames D and K system is shown in figure 1, in which the image signal amplitude modulates the image carrier frequency fp, and the phase characteristics of low frequency are maintained in the form of vestigial sideband. The frequency band of the image signal with partially suppressed lower sideband is -0.75 ~+6 MHz relative to fp, and the audio signal modulates the audio carrier frequency fs, which is 6.5MHz higher than the image carrier frequency, and the frequency range of the modulated audio signal is 0.25 MHz relative to fs. In this way, each TV channel occupies a frequency range of 8 MHz.

Color TV system

In addition to the same Latin alphabet distinguishing standard contents as black-and-white TV (Table 2), different color TV standards are formed according to different coding and decoding methods of tricolor signals at transmitter and receiver. Broadcast color TV system requires compatibility with black-and-white TV, that is, black-and-white TV can receive color TV broadcasts, and color TV can also receive black-and-white TV broadcasts, but all they receive are black-and-white images and accompanying sounds. Therefore, according to the principle of mixing a certain proportion of light energy of three primary colors into various colored lights including white light, in order to be compatible with and compress the transmission band, color TV sets generally combine three primary color signals of red (R), green (G) and blue (B-Y, R-Y) into one brightness signal (Y) and two color difference signals of blue and red (B-Y, R-Y), where the brightness signal can be. Therefore, compatible color TV not only transmits the same brightness signal and sound signal as black-and-white TV, but also transmits the chroma signal in the same video frequency band. The chroma signal is formed by two color difference signals modulating the color subcarrier at the high frequency end of the video frequency band. In order to prevent the modulation overload of the color difference signal, the blue and red difference signals (B-Y) and (R-Y) are compressed, and the compressed blue and red difference signals are represented by U and V. ..

1, NTSC 1954 A compatible color TV system was officially broadcast in the United States, and also used in Canada, Japan and other countries. NTSC stands for National Television System Committee. According to the visual characteristics that the human eye has the weakest ability to distinguish the color details of blue and magenta, but the strongest ability to distinguish the color details of red and yellow, this system uses the color difference signal Q of blue and magenta and the color difference signal I of red and yellow to replace the color difference signals U and V of blue and red ... The two color subcarriers with initial phase angles of 33 and123 are modulated by orthogonal balanced amplitude, respectively, to realize the decoding, separation and separation of subcarriers. The modulated two color difference signals are mixed to form a color signal. In order to detect the chroma signal synchronously at the receiving end, it is necessary to send a good synchronization signal at the sending end by using the line blanking period. The system has the characteristics of simple decoding circuit and low cost.

2.PAL system 1963 The system developed by the Federal Republic of Germany to reduce the phase sensitivity of NTSC system was officially broadcast in 1967, and it is also used in Britain and China. PAL is the abbreviation of phase substitution line. In this system, the U and V color difference signals are used to carry out orthogonal balanced amplitude modulation on two same-frequency color subcarriers with initial phases of 0 and 90 respectively, and the color difference signals of V components are inverted line by line. In this way, the phase deviation of the chrominance signal is cancelled by averaging between adjacent lines. The characteristics of this system are insensitive to phase deviation and less influenced by ghost color caused by multipath reception in transmission.

3.SECAM system 1967 was officially broadcast in France. It is also a compatible color TV system, aiming at improving the phase sensitivity of NTSC system. It is also used in the Soviet Union and some eastern European countries. SECAM is the abbreviation of Séquential Couleurà Mémoire, which means that when transmitting luminance and chrominance signals at the same time, the transmitter transmits red and blue difference signals line by line respectively. However, when decoding at the receiving end, it is necessary to have brightness and red-blue difference signals at the same time to restore red, green and blue signals. Therefore, in the receiving decoder, one of the received color difference signals is stored for one line by using a delay line, and then three signals for decoding are formed together with brightness (delayed by one line at the beginning) and another color difference signal received in the next line. Chroma signal is formed by frequency modulation of two color sub-carriers with a certain frequency interval by red and blue color difference signals. The characteristic of this system is that it is less affected by multipath reception in transmission.

4. Full TV signal is a composite signal of images transmitted in TV video baseband. The full TV signal of black-and-white TV includes: line (horizontal) in reverse scanning, field (vertical) scanning synchronization and blanking signal, and black-and-white brightness signal in forward scanning. Synchronous signals are synchronously received and scanned to ensure the stable reproduction of received images; Blanking signal is used to eliminate the interference of flyback bright line; The black-and-white brightness signal is used for black-and-white or color TV sets to receive black-and-white TV images. The full TV signal of color TV (Figure 2) is the same as that of black and white TV, and there are also color synchronization signals and chroma signals. Wherein the color burst signal is transmitted during the reverse scanning. In NTSC and PAL systems, it provides the frequency and phase reference of color subcarrier required by the receiving decoder. In SECAM system, it is used as a line sequence identification signal. Chrominance signals are transmitted simultaneously with black and white luminance signals during scanning, occupying a small part of the high-frequency end of the video baseband. After demodulation, two color difference signals are obtained. Black and white luminance signals occupy most of the video baseband above low frequency. In addition to receiving black and white images for black and white TV, it also enters the matrix network together with two color difference signals, and is restored to three primary color signals of red, green and blue, which are amplified and sent to the color picture tube to display color images.

[Edit this paragraph] A brief history of development

The invention of television

Television was not invented by anyone. It is the crystallization of a large group of people in different historical periods and different countries. As early as the19th century, people began to discuss and explore ways to convert images into electronic signals. 1900 The word "TV" appeared.

1On June 2nd, 925, John Logie Baird, a scot, scanned the image of a puppet in an experiment in London. People usually regarded him as the symbol of the birth of television, and he was called the "father of television". However, this view is controversial. Because, also in that year, American vladimir zworykin showed his TV system to his boss in Westinghouse.

Although the time is the same, the TV systems in John Logie Baird and vladimir zworykin are quite different. Historically, John Logie Baird's television system was called mechanical television, while Sforokin's system was called electronic television. This difference is mainly due to the different transmission and reception principles.

The development of television is complicated. Almost at the same time, many people are doing the same research.

American RCA 1939 introduced the world's first black-and-white TV set, 1953 formulated the national color TV standard, and 1954 introduced RCA color TV set.

The development of television

Christmas 1883

German electrical engineer Ni Pukov made the first experiment of emitting images by mechanical scanning with his invented "Ni Pukov disk". Each picture has 24 lines, and the image is quite blurred.

1908

Kemper Swinton of Britain and Roshenko of Russia did not put forward the principle of electronic scanning, which laid the theoretical foundation of modern electrical technology.

1923

Soviet Zvare blonde understood the electrostatic storage camera tube. The electronic scanning picture tube was invented in 1998 and is the pioneer of modern television photography.

1925

John Lodge Baird of Britain has made new research work based on the "Pukov disk" and invented the mechanical scanning TV camera and receiver. At that time, the resolution of the picture was only 30 lines, and the scanner could only scan the scanning area five times per second. The painting itself is only 2 inches high and 1 inch wide. Performing for the public in a big shop in London.

1926

Baird performed radio and television programs for the British press.

1927—— 1929

Baird first tried to broadcast electromechanical TV through telephone line; The first short-wave TV experiment; The BBC began to broadcast TV programs continuously for a long time.

1930

Realize the synchronous playback of TV images and sounds.

193 1 year

Put the movie on the TV screen for the first time. People watched the live broadcast of the famous local jockey club in Britain on TV in London. -The United States invented a kinescope television device that can reflect 25 images per second.

1936

The BBC adopted Baird's electromechanical television broadcasting, and broadcast high-definition television images for the first time, which entered the practical stage.

1939

American radio company began to broadcast all-electronic TV. Swiss Philip invented the first black-and-white TV projector.

1940

Gullmar Company of America has developed an electromechanical color TV system.

1949 12 17

The first television cable laid between London, England and Sutton Colfield was opened.

195 1 year

American H. Lowe invented the three-gun shadow mask color picture tube, and Lorenz invented the single-gun color picture tube.

1954

Texas Instruments developed the first all-transistor TV receiver.

1966

American radio company has developed integrated circuit TV sets. Three years later, a color TV receiver with electronic tuning device came out.

1972

Japan has developed a color TV projector.

1973

Digital technology is used in TV broadcasting, and experiments prove that digital TV can be used in satellite communication.

1976

Britain has completed the research of "TV Library" system, where users can directly consult news, books, newspapers or magazines with TV sets.

1977

Britain developed the first batch of portable TV sets.

1979

The world's first "cable TV" was opened in London. It was invented by the British Post Office. It can transmit the information in the computer through the ordinary telephone line and display it on the user's TV screen.

198 1 year

Sony Corporation of Japan has developed a pocket-sized black-and-white TV with a 2.5-inch LCD screen and battery power supply.

1984

Panasonic Corporation of Japan launched "Cosmic TV". The picture of the system is 3.6 meters wide and 4.62 meters high, which is equivalent to 2 10 inch. You can put it on a big truck and play in the streets and squares. The system adopts the "high brightness color LED" exclusively developed by Panasonic, which can obtain colorful images outdoors even during the day.

1985 March 17

At the Tsukuba Science Expo held in Japan, a super-large screen color TV wall built by Sony was unveiled. It is located in the central square, 40 meters long and 25 meters high, with an area of 1000 square meters. The whole building is as high as 14 floors. It is equivalent to a 1857 inch color TV. The super-large screen consists of 36 large luminous screens, each weighing 1 ton and being1.8m thick. 4 rows, 9 works, 450,000 color luminous elements. Through the camera installed at the top, you can show all kinds of activities at the venue at any time and play all kinds of advertising videos of Sony.

1985

British Telecom (BT) launched an integrated digital communication network. It provides users with voice, fast chart transmission, fax, slow scan television terminal and so on.

199 1 year165438+1October 25th.

The HDTV of Sony Corporation of Japan started trial broadcasting: its scanning line is 1 125, which is twice as much as the current 525, and the picture quality is improved by100%; The aspect ratio of the picture is changed from the traditional 9: 12 to 9: 16, which enhances the audience's sense of presence; The viewing angle of the tablet machine is extended from 10 to 30 degrees, which makes the map feel deeper; The "pixel" of TV has increased from 280,000 to 6.5438+0.27 million, and the amount of information per unit area has increased by nearly four times ... So the distance to watch HDTV is not seven times that of the screen in the past, but three times, and the sound is realistic, and the four-channel high-fidelity stereo is infectious.

1995

Sony Corporation of Japan introduced an ultra-miniature color TV receiver (that is, a handheld color TV), which is only the size of a palm and weighs 280 grams. There are speakers and earphone holes, and the LCD screen is about 5.5 cm. Although the picture looks small, the image is clear. Its most obvious feature is to use the human body as an antenna to get the viewing effect. When watching TV, you can get the effect similar to an outdoor antenna by putting two wires around your neck.

1996

Sony Corporation of Japan introduced a wall-mounted TV to the market: it is 60 cm long, 38 cm wide, 3.7 cm thick and weighs only 1.7 kg, just like a mural.

1September 2, 958

China began to broadcast black and white TV, and established the corresponding TV industry.

1973

Start the trial broadcast of color TV.

Development history of China TV manufacturing industry

1958, the first Taipei Jingpai 14 inch black and white TV set was born in Tianjin 7 12 factory.

1970 65438+On February 26th, the first color TV set in China was born in the same place, which opened the precedent for color TV production in China.

1978, the state approved the introduction of the first color TV production line and fixed it in the former Shanghai TV Machine Factory, which is now Shanghai Radio and Television Group. 1982 10 was completed and put into production. Soon, Xianyang Rainbow Factory, the first color tube factory in China, was established. During this period, the color TV industry in China has rapidly warmed up and formed a scale. More than 0/00 large and small color TV production lines have been introduced nationwide, and a large number of domestic brands such as Panda, Venus, Peony and Feiyue have emerged.

1985, China's TV production has reached16.63 million sets, surpassing the United States and becoming the second largest TV producer in the world after Japan. However, restricted by the structure, price and consumption power of China's TV market, the TV penetration rate is still very low, and the number of TVs per 100 households in urban and rural areas is only 17.2 and 0.8 respectively.

1987, China's TV production has reached19.34 million, surpassing Japan and becoming the largest TV producer in the world.

1985- 1993, the color TV market in China has achieved a large-scale upgrade from black-and-white TV to color TV.

1993 in the first half of the year, TCL began to launch the "TCL Ace" large-screen color TV. The market price of 29-inch color TV sets is around 6,000 yuan, and by the end of the year, 654.38 million sets have been sold.

1in March, 1996, Changhong announced its first large-scale price reduction to the whole country-the price of color TV sets was reduced by 8% to 18%. Two months later, Konka followed closely and started an unprecedented price war in the history of color TV industry. In April of that year, Changhong's sales jumped to the top of the market, and domestic brands seized a lot of market share of foreign brands through price wars. After the war, the price reduction also led to the reshuffle of the whole color TV industry in China, and dozens of color TV manufacturers withdrew from it.

1999, consumer-grade plasma color TV sets appeared in domestic shopping malls. At that time, the price of 40-inch plasma color TV was above100000 yuan.

In 200 1 year, China color TV industry suffered huge losses, while Konka, Xoceco and Gaoluhua suffered losses, and Changhong only earned 1 cent per share. This situation was not reversed until 2002 through technical upgrading.

In 2002, Changhong announced that it had successfully developed the first LCD TV with the largest screen in China. Its screen size greatly exceeds the traditional industry limit of 22 inches, and the screen size has reached 30 inches. At that time, it was called "China on the Fold".

In 2002, TCL launched the "popularization storm" of plasma TV, which opened the door for plasma TV to go to consumers' homes. Hisense immediately followed up.

In April 2003, Ni launched the popularization plan of rear projection TV, with the highest drop of 40%.

In 2004, the United States began to implement anti-dumping on China color TV sets, which made it impossible for China color TV sets to enter the American market directly.

In 2004, the total sales volume of color TVs in China was 35 million, of which the sales volume of flat-panel TVs was only 400,000, accounting for 1. 14% of the total color TV products.

Since June 5438+ 10, 2004, the sales of flat-panel TVs in several major cities in China have surpassed the traditional CRT (analog) color TVs for the first time.

In the first half of 2005, the sales volume of flat-panel color TVs in China reached 725,000 units, up 260% year-on-year. The ownership rate of LCD TV and plasma TV in urban households reached 3.56% and 2.8 1% respectively.

The present situation of television

Now, television is undergoing a revolution. Present situation of TV technology: One of the most obvious characteristics of TV technology is digitalization. The first is the digitization of program production. In the late 1990s, the British Broadcasting Corporation (BBC) took the lead in establishing the Columbus system in the world. The system makes the storage, editing and playing of BBC TV programs fully digital, that is, without tape, thus greatly improving the work efficiency of BBC and saving the production cost. In addition, the traditional analog cameras and video tapes are gradually being eliminated by the current television institutions, replaced by digital cameras and various emerging record carriers. This change has greatly improved the image quality. Secondly, the transmission technology is also diversified. In addition to the traditional wireless microwave transmission, there are now cable TV, satellite TV and other transmission methods. These new transmission modes effectively reduce the inevitable attenuation of signals during transmission and ensure better reception quality. Finally, the digital transformation of receiving technology. The improvement of sound quality and image quality and two-way interaction are the two biggest benefits brought by the wide popularization of digitalization.

The present situation of television. The TV set used by most people today is not much smaller than it was ten years ago. Because CRT technology is still the most commonly used display technology. The biggest disadvantage of this technology is that the size of the screen is proportional to the volume. And 34 inches is the maximum limit that this technology can reach. This obviously runs counter to people's needs. Therefore, more display technologies have emerged. Such as rear projection TV, LCD TV, plasma TV, etc. At the same time, with the digitalization of TV production and transmission technology, the digitalization of receiving equipment has become inevitable. Digital TV has better display effect and more functions, and can even realize preliminary two-way interaction. Another trend of TV is intelligence, that is, the combination with other electrical appliances, especially with computers. This will make TV more "intelligent" and have more functions, thus breaking through the traditional meaning of TV.

The rapid development of TV media makes people feel at a loss and more confused. Television media is seriously polarized. Well-known TV organizations such as BBC and CNN have strong voice, enhanced professionalism and narrower audience.

The future of television

There are two directions in the production of TV programs. One is more realistic. That is, the event itself is more truly restored. For example, CNN's extensive live broadcast of news events is one of them. The other is more dramatic. For example, contrary to CNN, Fox News used a lot of dramatic language in its program to "exaggerate" the American war against Iraq. Of course, the above two directions are just two different directions of program production, which have always existed. It's just that the characteristics have become more prominent recently. In addition, there are narrow programs and special channels.

At the same time, with the development of science and technology, TV is used by more and more countries as a tool. Because the current national strength is not limited to the traditional "hard" strength such as economy and military. Soft power such as culture should also be considered. Therefore, TV is considered as a good tool to enhance a country's soft power. At present, this trend is getting worse.

Television is a technology as well as a culture. When its cultural level is challenged by other emerging media (such as the Internet), its influence will inevitably decline as before. However, TV will develop greatly as a technology. In the future, TV technology will be more widely combined with other technologies, thus fully facilitating people's lives. For example, the recent combination of TV technology and mobile communication technology makes it possible to provide mobile TV in Norway first. A few years ago, the British Broadcasting Corporation (BBC) organically combined TV technology with the Internet, and turned its core website BBCi into a huge image database, making it at the forefront of the world media in terms of interactive ability.

[Edit this paragraph] TV classification

From the use effect and appearance, it can be roughly divided into four categories: flat-panel TV (plasma, LCD and some ultra-thin wall-mounted DLP rear projection) and CRT CRT TV (flat-panel CRT, ultra-flat CRT, ultra-thin CRT, etc.). ), rear projection TV (CRT rear projection, DLP rear projection, LCOS rear projection, LCD rear projection) and projection TV.

1. Flat-panel TV: The main advantages are that it is quite thin and can be hung on the wall, and their display screen can be made very large (at present, plasma can be more than 60 inches, and LCD can be more than 47 inches). But its disadvantage is that its viewing angle and reaction speed are limited to some extent, and its price is extremely expensive.

2.CRT picture tube TV (here only refers to digital high definition): The main advantages are excellent in all aspects (high brightness and contrast, large viewing angle, fast response and good color reproduction), but its screen is only about 34 inches at most, and it is very thick and bulky, and it also consumes a lot of power. But in comparison, the price is still very cheap.

3. Rear projection (CRT rear projection, DLP rear projection, LCOS rear projection, LCD rear projection): The traditional CRT rear projection is not very popular, and the market has been taken away by digital rear projection (DLP rear projection, LCOS rear projection, LCD rear projection). DLP light display rear projection is popular at present, because it can be said to be a real digital TV, with good performance in all aspects, large screen and small volume (we have said its imaging principle many times, welcome to Xinbao. com to find the answer), and it is the most popular one at present. LCD rear projection is slightly inferior because of its high calorific value and short bulb life.

4. Projection TV: In fact, it is the civilian projector we saw in the company meeting room, which is usually installed at home and can be used to watch movies.