There are TVs in almost every family. Whether it is used for terrestrial TV, or for displaying an image from YouTube or a game console – in any case, a large screen in the house is convenient. In this article, we look at the main stages through which these screens went through their development path.
Now it's hard to imagine a TV that would not use electronics. But it all started with the use of fairly simple mechanical devices.
The first important discovery in the history of TVs was made when German student Paul Gottlieb Nipkov studied in Neustadt. He missed his mother and very much wanted to see her on Christmas Eve. To realize his desire, he decided on the principle of telephone or telegraph, which already existed at that time. These reflections led him to the idea of a new device – a scanning disk, which was later named after him.
His invention was a rotating disk with holes spiraling. When rotating, each hole scanned its line. The number of rows, respectively, depended on the number of holes on the disk.
Formally, each line was part of a circle, but with a large ratio of the radius of the disk to the screen size, they could easily have been approximated to straight lines. By placing the photosensitive panel behind the disk, it was possible to obtain a picture with a resolution of lines equivalent to the number of holes on the disk.
In 1884, Paul Nipkov was granted a patent for his invention. This point can rightly be considered the beginning of the era of television. However, before using it not only for scanning, but also for image transmission, it was necessary to wait a few more decades, right up to the invention of a radio lamp.
The first television set
In the 1920s, the Scottish inventor John Louge Byrd experimented with two Nipkova disks in the hope of learning not only to scan, but also to transfer the image. The idea of his invention was to synchronize the rotation of two disks – one scanning, the other – reproducing. Behind the first disk was to be located photocell, and behind the second – a radio lamp. They, in turn, also had to be synchronized. When the photocell registered more intense light, the lamp had to glow brighter when the less intense – dimmer.
After a series of vain attempts, John Baird still managed to synchronize Nipkov disks. The first image he was able to reproduce with his instrument was the Maltese cross, whose outline could be unambiguously recognized on the reproduced picture.
One of the first images transmitted by Baird, which has survived to this day.
In 1923, John Baird received a patent for his invention, but at that time no one saw the potential in it. Not finding sponsors for further development, John had to slowly but surely develop his ideas on his own.
In 1928, the world saw the first commercial device called The Televisor. It was a large box with a huge disk and a screen that resembled the earpiece of a telephone of the time, to which it was necessary to apply not with an ear, but with the eye.
The Televisor (1930 model)
Over time, the resolution of the picture grew: the original 30 lines turned into 38, and then to 90 and even to 120. But this required all the larger disks that should were spinning faster. So mechanical TVs quickly reached their limit. The world needed a new breakthrough.
Simultaneously with mechanical TVs, electronic analogues developed. The principle of operation was based on the invention of Karl Ferdinand Brown, a German physicist, Nobel Prize winner. In 1897 he invented a cathode-ray tube. It was a glass flask with horizontal and vertical deflecting coils. By feeding current to the coils, a magnetic field was created which deflected the electron beam passing through them. Stronger current – stronger deviation. By feeding different currents to the vertical and horizontal coils, it was possible to accurately direct the electron beam to the selected point.
In 1923, two physicists, Vladimir Zvorykin and Filo Taylor Farnsworth practically simultaneously presented to the world a modified electron-beam tube, which was then used for many years TVs. Disputes about who is still a real CRT author have been going on for quite some time, and the results may vary depending on which country you ask this question in. The situation personally reminds me of the controversy about the Marconi or Popov championship in inventing a radio.
By the way, it's funny that it was with Marconi that Carl Brown, the inventor of a kinescope, received his Nobel Prize in Physics "for his contribution to the development of wireless telegraphy."
In televisions, a cathode-ray tube directed an electron beam to the fluorescent surface of the screen. Like mechanical TVs, the picture was drawn line by line. But since it did not need to rotate large disks, this could happen much faster than with a mechanical TV. In addition, the size limit of the screen has significantly widened.
CRT TVs came into the industry seriously and for a long time. Even now they are firmly entrenched in the names of things related to the screens. Many of us still refer to TV sets as "boxes", speaking even of the flattest panels, and the English analogue of the box, Tube (tube, tube), is imprinted in the most popular video service in the world.
The TVs with a kinescope dominated the market up to the beginning of the XXI century. All this time they actively developed. First the screens got color. By the way, one of the first broadcasts, showing the advantage of color television over black and white, was a snooker match. In this form of billiards, in addition to the white cue ball there are eight different colors of the balls: red, yellow, green, brown, blue, pink and black. In black and white, it was simply impossible to follow the game.
Then the CRT TVs became flat, and the cathode-ray tube itself became smaller in size and more energy efficient. But over time, this technology has reached its limit. With the growth of the screens, the TVs became much larger and heavier, the energy consumption increased significantly, and the resolution increased with the speed of electron beam movement on the screen.
After the cathode-ray tubes with TVs, so-called " flat panels. In fact, this is an abstract general definition of televisions whose screen area is much larger than the thickness.
During the transition from the CRT, several technologies have already been replaced, each of which occupied a significant position in the market in its time period.
Plasma screens really were based on the fact that they contained matter in the fourth aggregate state – the same plasma. The principle of operation of such screens was first introduced in the 1930s, and the first monochrome prototypes appeared in the 1960s. But the mass market, they came out only in the early 2000's.
The screen consisted of individual cells, located between two layers of glass. Inside the cell there is a plasma, an ionized gas in which ions fly freely, positively charged particles, and electrons, negatively charged particles. When electricity was passed through the plasma, it began to emit light, but this light was ultraviolet. That is, it could not be seen with the naked eye. Light in the visible spectrum was generated using a special fluorescent coating on each of the cells. When this coating is exposed to ultraviolet light, the cell itself begins to glow with the desired color already in the visible spectrum.
Plasma panels dominated the market for a long time, but eventually their shortcomings began to manifest themselves more and more. First, plasma screens lost in maximum brightness to competing technologies, which made it difficult to view in brightly lit rooms. In addition, physical dimensions remained the limiting factor. Plasma could not be made either large enough diagonally across the screen, nor thin enough. All this in combination with a complex production process and other factors led to the fact that in 2010 the manufacturers massively abandoned the technology in favor of LED and OLED.
Panels with backlighting
Backlit TVs are now the most popular by virtue of relative simplicity of production and, as a consequence, the cost of technology. The main principle of the operation of such screens is that behind the layer of liquid crystals (LCD) is illumination. Typically, the labeling of TVs depends on the mechanism of this very highlight. LCD-TVs are called panels with fluorescent, and LED-TVs – with LED. Although, in fact, both these types are LCD.
Liquid crystals themselves are molecules that can polarize light. In this case, depending on the electric current applied to them, they can rotate in space. The rotation angle depends on how much light they pass.
A typical pixel in the LED matrix consists of three sub-pixels: red, green and blue (RGB). Different colors are achieved by applying appropriate filters over the pixels. The voltage applied to each of the sub-pixels determines how much the "shutter" of each of the liquid crystals closes and, as a consequence, how many of each of the colors fall into the unit of the image.
Using this technology in mass production of TVs made it possible to significantly reduce the cost of the panels, they are bigger and thinner. At the moment, most TVs that can be bought work exactly on the principle of liquid crystals with backlighting.
Panels without backlighting
Logical continuation of LCD technology is OLED. It allows you to abandon the layer with backlighting, because the organic LEDs used in OLED screens can emit their own light.
This approach allows you to make screens even more subtle. For example, the most thin commercial TV panels from LG have a thickness of less than 4 mm. Even the 65-inch version is so lightweight that it does not require classic mounts. The TV is mounted on magnets to the metal surface on the wall.
A distinctive feature of OLED-screens is their maximum viewing angles. Even when viewed from the side, the brightness and contrast of the image are not reduced, and the colors are displayed as brightly and clearly as possible.
The unique WRGB matrix has a white subpixel in addition to the three basic colors, which allows to extend the life of the devices. Another obvious advantage of the lack of backlight is the high contrast that LCD panels do not have.
With the development of OLED technology, the range of images is constantly expanding, the accuracy and color saturation are enhanced, and the maximum brightness is achieved due to the HDR effect. Also worth noting is the improved technology of detail transfer in the darkest areas and the optimized uniformity of luminescence.
The fastest response time plays an enormous role in image quality – the high speed of the matrix response eliminates the blurring effect, resulting in unnecessary backgrounds.
The disadvantage of OLED-panels at the moment is the cost. So far, they occupy the upper segment of the market and it is not known when they can become more accessible.
As a result
The TVs have come a long way. A little less than a hundred years, the technology has made many steps from mechanical boxes with a viewing area of a couple of inches and a resolution of 20-30 lines to panels a few millimeters thick and up to 100 inches diagonals and a resolution of 4K or more.
The image quality is growing, new and new technologies are emerging. Who knows what the device will look like for the visual display of content in another hundred years.