Information output devices. LCD monitors

, a monitor based on the phenomenon of phosphor glow under the influence of ultraviolet rays that occur during an electrical discharge in an ionized gas, in other words, in a plasma. (See also: SED).

Story

Orange monochrome Digivue display panel in PLATO V, 1981

The plasma panel was developed at the University of Illinois during the creation of the US e-learning system by Dr. Donald Bitzer, H. Gene Slottow and Robert Willson. They received a patent for the invention in 1964. The first flat panel display consisted of a single pixel.

In 1971, Owens-Illinois acquired the license to manufacture Digivue displays. In 1983, the University of Illinois licensed the production of plasma panels to IBM.

The world's first 21-inch (53 cm) full-color display was introduced in 1992 by Fujitsu. In 1999, Matsushita (Panasonic) created a promising 60-inch prototype.

Since 2010, the production of plasma TVs has been declining due to the inability to compete with cheaper LED TVs, and in 2014 it practically ceased.

Design

Plasma panel device

A plasma panel is a matrix of gas-filled cells enclosed between two parallel glass plates, inside of which there are transparent electrodes that form scanning, illumination and addressing buses. The gas discharge flows between the discharge electrodes (scanning and backlight) on the front side of the screen and the addressing electrode on the back side.

Design Features:

• The plasma panel subpixel has the following dimensions: 200 x 200 x 100 µm;
• the front electrode is made of indium tin oxide because it conducts current and is as transparent as possible.
• when large currents flow through a fairly large plasma screen, due to the resistance of the conductors, a significant voltage drop occurs, leading to signal distortion, and therefore intermediate conductors made of chromium are added, despite its opacity;
• to create plasma, cells are usually filled with gases - neon or xenon (less commonly used helium and/or argon, or, more often, mixtures thereof) with the addition of .

Chemical composition of the phosphor:

The present problem of addressing millions of pixels is solved by arranging the front pair of tracks as rows (scan and backlight buses) and each rear track as columns (addressing bus). Plasma screens' internal electronics automatically select the correct pixels. This operation is faster than beam scanning on CRT monitors. In the latest PDP models, the screen refreshes at frequencies of 400 - 600 Hz, which allows the human eye not to notice screen flickering.

Operating principle

The operation of a plasma panel consists of three stages:

1. initialization, during which the position of the charges of the medium is ordered and prepared for the next stage (addressing). In this case, there is no voltage at the addressing electrode, and an initialization pulse, which has a stepped form, is applied to the scanning electrode relative to the backlight electrode. At the first stage of this pulse, the arrangement of the ionic gas medium is ordered, at the second stage there is a discharge in the gas, and at the third the ordering is completed.
2. addressing, during which the pixel is prepared for highlighting. A positive pulse is applied to the addressing bus (+75 IN), and the scan bus is negative (–75 V). On the backlight bus, the voltage is set to +150 V.
3. backlight, during which a positive pulse equal to 190 V is applied to the scanning bus and a negative pulse equal to 190 V is applied to the backlight bus. The sum of the ion potentials on each bus and additional pulses leads to exceeding the threshold potential and a discharge in a gaseous environment. After the discharge, the ions are redistributed at the scanning and illumination buses. Changing the polarity of the pulses leads to a repeated discharge in the plasma. Thus, by changing the polarity of the pulses, multiple discharges of the cell are ensured.

One cycle “initialization - addressing - illumination” forms one subfield of the image. By adding several subfields, it is possible to provide an image of a given brightness and contrast. In the standard version, each frame of the plasma panel is formed by adding eight subfields.

Thus, when high-frequency voltage is applied to the electrodes, gas ionization or plasma formation occurs. A capacitive high-frequency discharge occurs in the plasma, which leads to ultraviolet radiation, which causes the phosphor to glow: red, green or blue. This glow passes through the front glass plate and enters the viewer's eye.

Advantages and disadvantages

Advantages:

• high contrast;
• depth of colors;
• stable uniformity on black and white;
• longest service life (30 years) compared to LCD panels (7-10 years)

Flaws:

• higher power consumption compared to LCD panels;
• large pixels and, as a consequence, only fairly large plasma panels have sufficient screen resolution;
• screen burnout from a still image (memory effect), for example, from a TV channel logo. Occurs due to overheating of the phosphor and its subsequent evaporation. http://televizor-info.ru/wp-content/uploads/2013/08/22.jpg http://televizor-info.ru/wp-content/uploads/2013/08/11.jpg A similar effect is observed on OLED TVs (organic light-emitting diode screen). Burnt-out OLED screens http://www.mobiledevice.ru/Images/65/News_65860_6.jpg https://s8.hostingkartinok.com/uploads/images/2018/06/e7ea71b85f2867f13bb8cf630d50dddc.jpg

If you want to buy a modern TV model, then you need to choose the model especially carefully, since today there are many types. Mostly, buyers are interested in which TV is better: LCD or plasma? Before making a choice, you should not only compare all the advantages and disadvantages of these types of TV, but also find out. This is exactly what we will talk about today.

Once cathode ray tubes became a thing of the past, and TVs themselves became thinner and lighter, each manufacturing and display technology began to try to prove that it was the best. This competition, in turn, led to higher quality televisions and an attempt to lower prices. However, it is worth saying that the latter does not always work out, since what more modern device, the more there is in it various functions, interfaces, etc., and this automatically increases its cost, whatever one may say.

Plasma TV

Today there are not many companies involved in the production of plasma TVs. Fujitsu from Japan was the first to use this technology. Modern models of monitors, panels and displays are produced based on their technology. To date this technology is in great demand among buyers.

Before purchasing equipment, you should understand the difference between a plasma TV and a plasma panel. The plasma panel is a monitor to which you can connect DVD player or a flash drive for watching videos. At the same time, such equipment is not provided with a TV tuner, so if you want to buy a full-fledged TV, it is better to choose a model that does have it.

Buying plasma TV, choose models from well-known companies that provide a one-year warranty on their equipment. The greater the guarantee, the better device. It is also important to consider whether there is service center of this manufacturer in your city.

LCD TV

LCD displays appeared 20 years ago and quickly became popular among users. Today there are many models with a large diagonal, low weight and screen thickness. These parameters of the TV allow you, if desired, to install it using a bracket on the wall, on a special hanging shelf, or to build it into furniture and walls.

Such TVs are cheaper than plasma TVs with the same dimensions. In addition, such displays often have noticeably better color rendering and brightness than plasma models. This is due to the fact that such TVs have fairly good resolution.

Technological features of LCD TVs

Such a display consists of two plates and liquid crystals placed between them. Transparent polished plates have the same transparent electrodes through which voltage is transmitted to the matrix cells.

Liquid crystals between such plates are arranged in a special way. A beam of light passes through a polarizer installed near the plates, which turns at a right angle. This design is complemented by backlighting and a light filter with RGB colors.

To increase the speed of operation in these devices, special thin-film transistors, better known as TFT, are produced. Thanks to them, each cell is controlled separately. Because of this, the response speed can reach 8 milliseconds.

Technological features of plasma

Plasma also consists of the same plates with electrodes as LCD monitors. The difference is that instead of liquid crystals, the space between them is filled with inert gases such as argon, neon, xenon or their compounds. Each cell is colored with a specific phosphor, which determines the future color of the pixel. One cell is separated from another by a partition that does not allow ultraviolet radiation or light from the other cell to pass through. This ensures the maximum level of contrast is achieved, regardless of the intensity of external lighting.

When applying for specific cell voltage, it begins to glow with the color in which its phosphor is painted. The difference between such TVs and LCDs is that each of the cells itself emits light, so the backlight of such a display is not required.

Comparative characteristics of plasma and liquid crystal panels

Characteristic	Winner	Details
Screen size		Not so long ago, large-diagonal LCD TVs practically did not exist, and plasma TVs were the undisputed winner, so the question of choosing plasma or LCD did not arise. But time passes and today LCD models have almost caught up with plasma. Therefore, the difference according to this criterion has disappeared and it is very difficult to determine the winner.
Contrast		This happens due to the fact that plasma TVs themselves emit light, which makes the image better and more saturated.
Glare in bright light		The brightness of the lamp backlight allows you to see the image on the screen even in bright lighting or direct sunlight. Plasma panels will produce glare.
Black depth		The reason for the loss of an LCD TV in this parameter is the same. Due to the additional illumination, the black is less deep than that of plasma, where its depth is achieved due to the fact that there is simply no electricity flowing to a given cell.
Fast response		Electricity is transmitted almost instantly through inert gas, so there are no problems. But with older models of LCD displays, shadows could appear when the picture was moving quickly. But today, thanks to TFT technology, the response speed in such TVs has decreased to 8 milliseconds. Therefore, if you choose a new TV model, you will not notice any artifacts.
Viewing angle		Plasma TVs started with a viewing angle of 160 degrees, but an older LCD TV model can have a viewing angle of only 45 degrees. But if you choose one of the modern models, then you shouldn’t worry, since today the viewing angle is LCD TVs and plasma – the same.
Illumination Uniformity		In plasma TVs, uniformity of illumination is ensured by the fact that each of the pixels is itself a light source and glows in the same way as the others. On LCD TVs, lighting uniformity depends on the lamp, but uniformity is still difficult to achieve.
Screen burn-in		Screen burn-in mainly affects plasma displays when viewing a static image. Over time, all objects may develop non-existent shadows, which is actually fixable. This is a common problem with devices containing phosphorus. IN LCD monitors it does not exist, and, therefore, such a problem does not threaten them.
Energy efficiency		LCD TVs consume almost 2 times less electricity than plasma TVs. This is due to the fact that the main amount of energy in plasma TVs is spent on cooling and powerful fans, but in LCD panels, practically nothing is used except the lighting lamp.
Durability		For LCD TV, the service life can reach up to 100,000 hours, while plasma has no more than 60,000 hours. In addition, for LCD screens this figure means the resource of the backlight lamp, and for plasma - the resource of the matrix. If you choose plasma, by the time those 60,000 hours have passed, the screen brightness will be half as bright.
Compatibility		In principle, both plasma and liquid crystal modern TVs there is enough variety of functions and interfaces. This may also be the ability to connect various game consoles, audio systems, Smart TV and 3D functions. However, LCD displays win due to the fact that they are best suited for use with a computer. They are better visible various schemes and graphics, as there are more pixels per inch than plasma monitors.
Price		Plasma TV on this moment cost significantly more than liquid crystal models with the same diagonal.

As a result, we can say that plasma panels have better color reproduction and response speed, while liquid crystal models are more energy efficient, durable and not subject to screen burnout. Therefore, before choosing what you need: LCD or plasma, decide what is most important for you in such a device.

Frame

Indicators

Indicators are installed mainly on computers and peripheral devices. They are different LEDs, small screens, or are borrowed from other devices. A simple example of an indicator would be an ammeter placed on a wire going to the hard drive. When working with memory, the arrow will move. But the indicator can serve, in addition to a decorative and informative function - the temperature sensor inside the system unit will tell you if the computer is overheating. The most complex indicator systems are assembled on a microcontroller and contain a display capable of showing text and even graphics, sometimes in color. Designing such circuits is quite difficult. Textbooks will help you with this difficult task. digital technology and microcontrollers.

Sometimes, to realize a creative idea, a modder makes a decision instead of a remake existing building buy another, more beautiful one, or even make a new one (sometimes using parts of an existing one). Often, especially when using miniature motherboards specially designed for modding (for example, Mini-ITX), the computer is assembled in a case from some other technical device, for example, a vacuum cleaner (such a mod actually exists). Interesting solution is the use of a completely transparent body. Because pre-made clear housings are expensive (about $150), they are often made from scratch. When making a case, you need to remember that metal is used for a reason. The computer generates a lot of radio interference, and the metal case absorbs it. A transparent case may interfere with the performance of radios, televisions, and high-end audio equipment near the computer, so be prepared to shield the case. The same applies to wooden cases. In some countries (not Russia), non-metallic housings are prohibited.

Monitors

The age of cathode ray tube monitors is inevitably becoming a thing of the past. Incredibly, in just six months, multi-page magazine reviews the latest models traditional monitors have given way to detailed descriptions of the properties of flat-panel displays, primarily liquid crystal displays, and now plasma. Yes, technology does not stand still, and now plasma, the highest energy state of matter, works where lightning speed of information exchange, amazing efficiency, and dazzling novelty are required. However, the commercial cycle of any invention does not last forever, and now manufacturers who have launched mass production of LCD panels are preparing the next generation of information imaging technologies. The devices that will replace liquid crystal ones are at different stages of development. Some, such as LEP (Light Emitting Polymer), are just emerging from scientific laboratories, while others, such as those based on plasma technology, are already complete commercial products. Although the plasma effect has been known to science for quite some time (it was discovered in the laboratories of the University of Illinois in 1966), plasma panels appeared only in 1997 in Japan. Why did it happen? This is due to both the high cost of such displays and their noticeable “gluttony” - power consumption. Although the technology for manufacturing plasma displays is somewhat simpler than liquid crystal displays, the fact that it has not yet been put into production helps maintain high prices for this still exotic product. Incomparable image quality and unique design features make information panels based on plasma technology especially attractive for the government and corporate sectors, healthcare, education, and the entertainment industry.

Based on the method of image formation, monitors can be divided into two groups:

• LCD screens
• Plasma displays
• Cathode ray tube (CRT)

Plasma displays.

The development of plasma displays, which began in 1968, was based on the use of the plasma effect, discovered at the University of Illinois in 1966.
Now the operating principle of the monitor is based on plasma technology: the glow effect of an inert gas under the influence of electricity is used (in much the same way as neon lamps work). Note that the powerful magnets that make up the dynamic sound emitters located next to the screen do not affect the image in any way, since plasma devices(as in LCD) there is no such thing as an electron beam, and at the same time all the elements of the CRT, which are so affected by vibration.

The formation of an image in a plasma display occurs in a space approximately 0.1 mm wide between two glass plates, filled with a mixture of noble gases - xenon and neon. The thinnest transparent conductors, or electrodes, are applied to the front, transparent plate, and mating conductors are applied to the back plate. By applying electrical voltage to the electrodes, it is possible to cause a gas breakdown in the desired cell, accompanied by the emission of light, which forms the required image. The first panels, filled mainly with neon, were monochrome and had a characteristic orange color. The problem of creating a color image was solved by applying phosphors of primary colors - red, green and blue - in triads of neighboring cells and selecting a gas mixture that, when discharged, emitted ultraviolet invisible to the eye, which excited the phosphors and created already visible color image(three cells per pixel).

However, traditional plasma screens on panels with direct current discharge also have a number of disadvantages caused by the physics of the processes occurring in this type bit cell.

The fact is that despite the relative simplicity and manufacturability of the DC panel, the weak point is the discharge gap electrodes, which are subject to intense erosion. This significantly limits the service life of the device and does not allow achieving high image brightness, limiting the discharge current. As a result, it is not possible to obtain a sufficient number of shades of color, typically limited to sixteen gradations, and speed suitable for displaying a full-fledged television or computer image. For this reason, plasma screens were commonly used as signboards to display alphanumeric and graphical information.

The problem can be fundamentally solved at the physical level by applying a dielectric material to the discharge electrodes. protective coating. However, such a simple solution at first glance radically changes the principle of operation of the entire device. The applied dielectric not only protects the electrodes, but also prevents the flow of discharge current. In fact, a system of electrodes coated with a dielectric forms a complex capacitor through which current pulses flow with a duration of about hundreds of nanoseconds and an amplitude of tens of amperes at the moments of its recharging. At the same time, the control algorithm becomes more complex and quite high-frequency. The repetition rate of complex-shaped pulses can reach two hundred kilohertz. All this significantly complicates the circuitry of the control system, however, it makes it possible to increase the brightness and durability of the screen by more than an order of magnitude and makes it possible to display full-color television and computer image with standard frame rates.

Modern plasma displays used as computer monitors (and the design is not typesetting) use the so-called technology - plasmavision - this is a set of cells, in other words, pixels, which consist of three subpixels that transmit colors - red, green and blue.

The gas in plasma state is used to react with phosphorus in each subpixel to produce a color (red, green or blue). A pixel in a plasma (gas-discharge) display resembles a conventional fluorescent lamp - ultraviolet radiation from an electrically charged gas hits the phosphor and excites it, causing a visible glow. In some designs, the phosphor is applied to the front surface of the cell, in others - to the back, and the front surface is made transparent. Each subpixel is individually controlled electronically and produces more than 16 million different colors. IN modern models each individual point of red, blue or Green colour can glow at one of 256 brightness levels, which when multiplied gives about 16.7 million shades of a combined color pixel (triad). In computer jargon, this color depth is called “True Color” and is considered quite sufficient to convey a photographic quality image. Conventional CRTs give the same amount. The latest screen brightness is 320 cD per square meter with a contrast ratio of 400:1. A professional computer monitor gives 350 cD, and a TV - from 200 to 270 cD per square meter with a contrast of 150...200:1.

This diagram gives short review plasma technology. Diagram components:

1. Electrical discharge stage
2. Emitter excitation stage

1. Outer glass layer
2. Dielectric layer
3. Layer of Protection
4. Display (receive) electrode
5. Unloading surface
6. Ultra-violet rays
7. Visible light
8. Barrier barrier
9. Fluorescence (glow)
10. Address Electrode (cornering)
11. Dielectric layer
12. Inner glass layer

It is convenient to present the technology of plasma monitors in the form of the following diagram:

The screen has the following functionality and characteristics:

• Wide viewing angle both horizontally and vertically (160° degrees or more).
• Very fast response time (4 µs per line).
• High purity color (equivalent to the purity of the three primary colors of a CRT).
• Ease of production of large-format panels (unattainable with thin film technological process).
• Thin - The gas discharge panel is about one centimeter or less thick, with the control electronics adding a few more centimeters;
• No geometric image distortion.
• Wide temperature range.
• Mechanical strength.

The introduction of two new technological structures, resistor and phosphor, made it possible to obtain the brightness and service life of the screen at the level required for practical applications. New photolithographic technology, as well as the stunblasting method, made it possible to produce a 40-inch plasma panel with high precision.

Main advantages.

Recently, when creating information display systems for various types of control rooms, gas plasma displays (plasma panels) have begun to be used. Plasma displays (PDP) are one of the latest developments in the field of information display systems (the first PDPs appeared in Japan in 1997). Thus, plasma panels are far superior in image quality to even good picture tubes, which are considered the standard in our time. It is very important that plasma panels are absolutely harmless to health, unlike cathode ray tubes.

It is clear that they are replacing existing cathode ray tube monitors due to obvious advantages, such as:

• Compact (depth does not exceed 10 - 15 cm) and light with fairly large screen sizes (40 - 50 inches).
• Thin - The gas discharge panel is about one centimeter or less thick, with the control electronics adding a few more centimeters.
• High speed upgrades (about five times better than an LCD panel).
• No flickering or blurring of moving objects that occurs during digital processing. since there is no screen blanking during the flyback period, as in a CRT.
• High brightness, contrast and clarity without geometric distortion.
• The absence of problems of electron beam convergence and focusing is inherent in all flat panel displays.
• No uneven brightness across the screen field.
• 100% use of screen area for images.
• Large viewing angle reaching 160° or more.
• Absence of X-rays and other radiation harmful to health, since high voltages are not used.
• Immunity to magnetic fields.
• Do not suffer from vibration like CRT monitors.
• No need to adjust the image.
• Mechanical strength.
• Wide temperature range.
• The short response time (the time between sending a signal to change the brightness of a pixel and the actual change) allows them to be used for displaying video and television signals.
• Higher reliability.

The plasma screen can be filmed with a video camera, and the picture does not shake, since a different principle of displaying information is used

All this makes plasma displays very attractive for use. Disadvantages include the limited resolution of most existing plasma monitors, which does not exceed 640x480 pixels. The exception is the PDP-V501MX and 502MX from Pioneer. Providing a real resolution of 1280x768 pixels, this display has the maximum screen size to date of 50 inches diagonally (110x62 cm) and good indicator in brightness (350 Nit), due to new technology cell formation, and improved contrast. As a result, this device allows:

• Display computer information with real XGA resolution (1024x768).
• Ensure comfortable surveillance of video information at a distance of up to 5 meters.
• Provide an image contrast of about 20 at a screen ambient light level of 150 - 200 Lux.

Thus, from our point of view, such displays are already suitable for professional use. However, it should be borne in mind that despite significant differences in technology, plasma displays use the same phosphor as cathode ray tubes, which, unlike CRTs, is excited not by electrons, but by ultraviolet radiation from a gas discharge and is also subject to degradation, although in to a lesser extent. Various manufacturers name the resource from 15,000 hours (NEC) to 20,000-30,000 (Pioneer) hours according to the criterion of reducing the brightness by half.

Since the image is static in nature, special measures have been taken to protect the displays from burn-in. IN in this case a special software, installed on control computers, allowing for “orbiting,” i.e., slow, invisible to the observer’s eye, circular movement of the image, which allows extending the service life of plasma displays several times. Hardware implementation of this function is also possible. Exist special devices, for example the VS-200-SL from Extron Electronics, which implement “orbiting” even synchronously on several displays. However, it should be kept in mind that the effectiveness this method Protection of plasma displays from burnout is realized only if certain requirements for the nature of the image are met. In particular, the background of the image should not be white.

Main disadvantages.

Disadvantages include the limited resolution of most existing plasma monitors, which does not exceed 640x480 pixels. The exception is the PDP-V501MX and 502MX from Pioneer. Providing a real resolution of 1280x768 pixels, this display has the current maximum screen size of 50 inches diagonally (110x62 cm) and a good brightness rating (350 Nit), due to new cell formation technology, and improved contrast.

The disadvantages of plasma displays also include the impossibility of “stitching” several displays into a “video wall” with an acceptable gap due to the presence of a wide frame around the perimeter of the screen

The fact that commercial plasma panel sizes typically start at forty inches suggests that producing smaller displays is not economically feasible, so we are unlikely to see plasma panels in, say, laptop computers. This assumption is supported by another fact: the level of energy consumption of “plasma machines” implies connecting them to the network and does not leave any possibility of operating on batteries. Another unpleasant effect known to specialists is interference, the “overlapping” of microdischarges in adjacent screen elements. As a result of such “mixing,” the image quality naturally deteriorates.

Also, the disadvantages of plasma displays include the fact that, for example, the average white brightness of plasma displays is currently about 300 cd/m2 for all major manufacturers. Overall this is quite bright, but plasma displays are nowhere near the 700 cd/m2 brightness of CRTs. Similar brightness can be achieved by increasing the luminous efficiency from 0.7 - 1.1 to 2 lm/W, but this level will not be easy to overcome. And now one cannot help but notice the very high price of plasma displays, which are not available to everyone.

LCD screens.

A liquid crystal is a state in which a substance has some of the properties of both a liquid (fluidity) and a solid crystal (for example, anisotropy). For the manufacture of LCD screens, so-called nematic crystals are used, the molecules of which have the shape of rods or elongated plates. In addition to crystals, the LCD element includes transparent electrodes and polarizers. In the absence of an electric field, the molecules of nematic crystals form twisted spirals. When a light beam passes through the LCD element at this moment, its plane of polarization rotates through a certain angle. If polarizers are placed at the input and output of this element, offset from each other by the same angle, then light can pass through this element without hindrance. If a voltage is applied to the transparent electrodes, the spiral of molecules straightens and the rotation of the plane of polarization no longer occurs. As a result, the output polarizer does not transmit light. An example is the LCD indicator of an electronic watch.
The LCD screen is a matrix of LCD elements. Currently, there are two main methods of addressing LCD elements: direct (or passive) and indirect (or active). In a passive matrix of LCD elements, the selected image point is activated by applying voltage to the corresponding transparent address conductors-electrodes of the row and column. In this case, it is impossible to achieve high image contrast, since the electric field arises not only at the point of intersection of the address conductors, but also along the entire path of current propagation. This problem is completely solvable when using the so-called active matrix of LCD elements, when each image point is controlled by its own electronic switch. The contrast when using an active matrix of LCD elements can reach values ​​from 50:1 to 100:1. Typically, active matrices are implemented on the basis of thin film field-effect transistors (Thin Film Transistor, TFT). A kind of compromise between the active and passive matrix are currently screens that use dual scanning technology (Dual Scan, DSTN), in which two lines of the image are simultaneously updated.

On the front side of the screen and with address electrodes running along its back side. The gas discharge produces ultraviolet radiation, which in turn initiates the visible glow of the phosphor. In color plasma panels, each pixel of the screen consists of three identical microscopic cavities containing an inert gas (xenon) and having two electrodes, front and back. Once a strong voltage is applied to the electrodes, the plasma will begin to move. At the same time, it emits ultraviolet light, which hits the phosphors in the lower part of each cavity. Phosphors emit one of the primary colors: red, green or blue. The colored light then passes through the glass and enters the viewer's eye. Thus, in plasma technology, pixels work like fluorescent tubes, but creating panels from them is quite problematic. The first difficulty is the pixel size. A plasma panel's sub-pixel has a volume of 200 µm x 200 µm x 100 µm, and several million pixels need to be stacked on the panel, one to one. Secondly, the front electrode should be as transparent as possible. Indium tin oxide is used for this purpose because it is conductive and transparent. Unfortunately, plasma panels can be so large and the oxide layer so thin that when large currents flow across the resistance of the conductors there will be a voltage drop that will greatly reduce and distort the signals. Therefore, it is necessary to add intermediate connecting conductors made of chromium - it conducts current much better, but, unfortunately, is opaque.

Finally, you need to choose the right phosphors. They depend on the required color:

• Green: Zn 2 SiO 4:Mn 2+ / BaAl 12 O 19:Mn 2+
• Red: Y 2 O 3:Eu 3+ / Y0.65Gd 0.35 BO 3:Eu 3
• Blue: BaMgAl 10 O 17:Eu 2+

These three phosphors produce light with wavelengths between 510 and 525 nm for green, 610 nm for red and 450 nm for blue. The last problem What remains is the addressing of pixels, since, as we have already seen, in order to obtain the required shade, you need to change the color intensity independently for each of the three sub-pixels. On a 1280x768 pixel plasma panel there are approximately three million sub-pixels, resulting in six million electrodes. As you can imagine, laying out six million tracks to control the sub-pixels independently is not possible, so the tracks must be multiplexed. The front tracks are usually lined up in solid lines, and the back tracks in columns. The electronics built into the plasma panel, using a matrix of tracks, selects the pixel that needs to be lit on the panel. The operation occurs very quickly, so the user does not notice anything - similar to beam scanning on CRT monitors.

A little history.

The first plasma display prototype appeared in 1964. It was designed by University of Illinois scientists Bitzer and Slottow as an alternative to the CRT screen for the Plato computer system. This display was monochrome and did not require additional memory or complex electronic circuits and was highly reliable. Its purpose was mainly to display letters and numbers. However, it never had time to be realized as a computer monitor, since thanks to semiconductor memory, which appeared in the late 70s, CRT monitors turned out to be cheaper to produce. But plasma panels, due to the shallow depth of the case and big screen have become widespread as information boards at airports, train stations and stock exchanges. IBM was heavily involved in information panels, and in 1987, Bitzer's former student, Dr. Larry Weber, founded the company Plasmaco, which began producing monochrome plasma displays. The first 21" color plasma display was introduced by Fujitsu in 1992. It was developed jointly with the design bureau of the University of Illinois and NHK. And in 1996, Fujitsu bought the Plasmaco company with all its technologies and plant, and launched the first commercially successful plasma panel on the market – Plasmavision with a 42" diagonal 852 x 480 resolution screen with progressive scan. The sale of licenses to other manufacturers began, the first of which was Pioneer. Subsequently, actively developing plasma technology, Pioneer, perhaps more than anyone else, succeeded in the plasma field, creating a number of excellent plasma models.

With all the stunning commercial success of plasma panels, the image quality at first was, to put it mildly, depressing. They cost incredible amounts of money, but quickly won an audience due to the fact that they differed favorably from CRT monsters with a flat body, which made it possible to hang the TV on the wall, and screen sizes: 42 inches diagonally versus 32 (maximum for CRT TVs). What was the main defect of the first plasma monitors? The fact is that, despite all the colorfulness of the picture, they were completely unable to cope with smooth color and brightness transitions: the latter disintegrated into steps with torn edges, which looked doubly terrible in a moving image. One could only guess why this effect arose, about which, as if by agreement, not a word was written by the media, which praised the new flat displays. However, after five years, when several generations of plasma had changed, steps began to appear less and less often, and in other indicators the image quality began to increase rapidly. In addition, in addition to 42-inch panels, 50" and 61" panels appeared. The resolution gradually increased, and somewhere during the transition to 1024 x 720, plasma displays were, as they say, in their prime. More recently, plasma has successfully crossed a new threshold of quality, entering the privileged circle of Full HD devices. Currently, the most popular screen sizes are 42 and 50 inches diagonally. In addition to the standard 61", a size of 65" has appeared, as well as a record 103". However, the real record is only to come: Matsushita (Panasonic) recently announced a 150" panel! But this, like the 103" models (by the way, the famous American company Runco produces plasma based on Panasonic panels of the same size), is an unbearable thing, both in the literal and even more literal sense (weight, price).

Plasma panel technologies.

Just something complicated.

Weight was mentioned for a reason: plasma panels weigh a lot, especially large models. This is due to the fact that the plasma panel is mainly made of glass, apart from the metal chassis and plastic body. Glass is necessary and irreplaceable here: it stops harmful ultraviolet radiation. For the same reason, no one produces fluorescent lamps made of plastic, only glass.

The entire design of a plasma screen is two sheets of glass, between which there is a cellular structure of pixels consisting of triads of subpixels - red, green and blue. The cells are filled with inert, so-called. “noble” gases - a mixture of neon, xenon, argon. An electric current passing through the gas causes it to glow. Essentially, a plasma panel is a matrix of tiny fluorescent lamps controlled by the panel's built-in computer. Each pixel cell is a kind of capacitor with electrodes. An electrical discharge ionizes gases, turning them into plasma - that is, an electrically neutral, highly ionized substance consisting of electrons, ions and neutral particles. In fact, each pixel is divided into three subpixels containing red (R), green (G) or blue (B) phosphor: Green: Zn2SiO4:Mn2+ / BaAl12O19:Mn2+ Red: Y2O3:Eu3+ / Y0.65Gd0.35BO3:Eu3 Blue : BaMgAl10O17:Eu2+ These three phosphors produce light with wavelengths between 510 and 525 nm for green, 610 nm for red and 450 nm for blue. In fact, the vertical rows R, G and B are simply divided into separate cells by horizontal constrictions, which makes the screen structure very similar to a mask kinescope regular TV. The similarity with the latter is that it uses the same colored phosphorus that coats the subpixel cells from the inside. Only the phosphorus phosphor is ignited not by an electron beam, as in a kinescope, but by ultraviolet radiation. To create a variety of color shades, the light intensity of each subpixel is controlled independently. IN CRT TVs this is done by changing the intensity of the flow of electrons, in `plasma` - using 8-bit pulse code modulation. The total number of color combinations in this case reaches 16,777,216 shades.

How light is made. The basis of each plasma panel is plasma itself, i.e. a gas consisting of ions (electrically charged atoms) and electrons (negatively charged particles). Under normal conditions, the gas consists of electrically neutral, i.e., particles without a charge.

If you introduce a large number of free electrons into a gas by passing an electric current through it, the situation changes radically. Free electrons collide with atoms, “knocking out” more and more electrons. Without an electron, the balance changes, the atom acquires a positive charge and turns into an ion.

When an electric current passes through the resulting plasma, the negatively and positively charged particles move towards each other.

Amid all this chaos, particles are constantly colliding. The collisions 'excite' the gas atoms in the plasma, causing them to release energy in the form of photons in the ultraviolet spectrum.

When photons hit the phosphor, the particles of the latter become excited and emit their own photons, but they will already be visible and take the form of light rays.

Between the glass walls are hundreds of thousands of cells coated with a phosphor that glows in red, green and blue. Beneath the visible glass surface - all along the screen - are long, transparent display electrodes, insulated on top with a sheet of dielectric and below with a layer of magnesium oxide (MgO).

For the process to be stable and controllable, it is necessary to provide a sufficient number of free electrons in the gas column plus a sufficiently high voltage (about 200 V), which will force the ion and electron flows to move towards each other.

And for ionization to occur instantly, in addition to control pulses, there is a residual charge on the electrodes. Control signals are supplied to the electrodes via horizontal and vertical conductors, forming an address grid. Moreover, the vertical (display) conductors are conductive paths on the inner surface of the protective glass from the front side. They are transparent (a layer of tin oxide mixed with indium). Horizontal (address) metal conductors are located on the back side of the cells.

Current flows from the display electrodes (cathodes) to the anode plates, which are rotated at 90 degrees relative to the display electrodes. The protective layer serves to prevent direct contact with the anode.

Under the display electrodes are the already mentioned RGB pixel cells, made in the form of tiny boxes, coated on the inside with a colored phosphor (each “color” box - red, green or blue - is called a subpixel). Below the cells is a structure of address electrodes positioned at 90 degrees to the display electrodes and passing through the corresponding color subpixels. Next is a protective level for the address electrodes, covered by the rear glass.

Before the plasma display is sealed, a mixture of two inert gases - xenon and neon - is injected into the space between the cells under low pressure. To ionize a specific cell, a voltage difference is created between the display and address electrodes located opposite each other above and below the cell.

A little reality.

In fact, the structure of real plasma screens is much more complex, and the physics of the process is not at all so simple. In addition to the matrix grid described above, there is another type - co-parallel, which provides an additional horizontal conductor. In addition, the thinnest metal tracks are duplicated to equalize the potential of the latter along the entire length, which is quite significant (1 m or more). The surface of the electrodes is covered with a layer of magnesium oxide, which performs an insulating function and at the same time provides secondary emission when bombarded with positive gas ions. There are also different types of pixel row geometry: simple and “waffle” (cells are separated by double vertical walls and horizontal bridges). Transparent electrodes can be made in the form of a double T or a meander, when they seem to be intertwined with the address electrodes, although they are in different planes. There are many other technological tricks aimed at increasing the efficiency of plasma screens, which was initially quite low. For the same purpose, manufacturers vary the gas composition of the cells, in particular, they increase the percentage of xenon from 2 to 10%. By the way, the gas mixture in the ionized state glows slightly on its own, therefore, in order to eliminate contamination of the spectrum of the phosphors by this glow, miniature light filters are installed in each cell.

Signal control.

The last problem remains the addressing of pixels, since, as we have already seen, in order to obtain the required shade, you need to change the color intensity independently for each of the three subpixels. On a 1280x768 pixel plasma panel there are approximately three million subpixels, resulting in six million electrodes. As you can imagine, laying out six million tracks to control the subpixels independently is not possible, so the tracks must be multiplexed. The front tracks are usually lined up in solid lines, and the back tracks in columns. The electronics built into the plasma panel, using a matrix of tracks, selects the pixel that needs to be lit on the panel. The operation occurs very quickly, so the user does not notice anything - similar to beam scanning on CRT monitors. Pixels are controlled using three types of pulses: starting, supporting and damping. The frequency is about 100 kHz, although there are ideas for additional modulation of control pulses with radio frequencies (40 MHz), which will ensure a more uniform discharge density in the gas column.

In fact, the control of pixel lighting is in the nature of discrete pulse-width modulation: the pixels glow exactly as long as the supporting pulse lasts. Its duration with 8-bit encoding can take 128 discrete values, respectively, the same number of gradations of brightness is obtained. Could this be the reason for the torn gradients breaking up into steps? Plasma of later generations gradually increased the resolution: 10, 12, 14 bits. The latest Runco Full HD models use 16-bit signal processing (probably encoding as well). One way or another, the steps have disappeared and, hopefully, will not appear again.

In addition to the panel itself.

Not only the panel itself was gradually improved, but also signal processing algorithms: scaling, progressive conversion, motion compensation, noise suppression, color synthesis optimization, etc. Each plasma manufacturer has its own set of technologies, partially duplicating others under other names, but partially their own. Thus, almost everyone used DCDi Faroudja scaling and adaptive progressive transformation algorithms, while some ordered original developments (for example, Vivix from Runco, Advanced Video Movement from Fujitsu, Dynamic HD Converter from Pioneer, etc.). In order to increase contrast, adjustments were made to the structure of control pulses and voltages. To increase brightness, additional jumpers were introduced into the shape of the cells to increase the surface covered with phosphor and reduce the illumination of neighboring pixels (Pioneer). The role of “intelligent” processing algorithms gradually grew: frame-by-frame optimization of brightness, a dynamic contrast system, and advanced color synthesis technologies were introduced. Adjustments to the original signal were made not only based on the characteristics of the signal itself (how dark or light the current scene was or how fast objects were moving), but also on the level of ambient light, which was monitored using a built-in photosensor. With the help of advanced processing algorithms, fantastic success has been achieved. Thus, Fujitsu, through an interpolation algorithm and corresponding modifications to the modulation process, has achieved an increase in the number of color gradations in dark fragments to 1019, which far exceeds the screen’s own capabilities with the traditional approach and corresponds to the sensitivity of the human visual system (Low Brightness Multi Gradation Processing technology). The same company developed a method of separate modulation of even and odd control horizontal electrodes (ALIS), which was then used in models from Hitachi, Loewe, etc. The method gave increased clarity and reduced jaggedness of inclined contours even without additional processing, and therefore, in the specifications of those using his plasma models had an unusual resolution of 1024 × 1024. This resolution, of course, was virtual, but the effect turned out to be very impressive.

Advantages and disadvantages.

Plasma is a display that, like a CRT TV, does not use light valves, but emits already modulated light directly by phosphorus triads. This, to a certain extent, makes plasma similar to cathode ray tubes, which are so familiar and have proven their worth over several decades.

Plasma has a noticeably wider coverage of the color space, which is also explained by the specifics of color synthesis, which is formed by “active” phosphorus elements, and not by passing the light flux of the lamp through light filters and light valves.

In addition, the plasma resource is about 60,000 hours.

So, plasma TVs are:

Large screen size + compactness + no flickering element; - High definition image; - Flat screen without geometric distortion; - Viewing angle 160 degrees in all directions; - The mechanism is not affected by magnetic fields; - High resolution and image brightness; - Availability of computer inputs; - 16:9 frame format and progressive scan mode.

Depending on the rhythm of the pulsating current that is passed through the cells, the intensity of the glow of each subpixel, which was controlled independently, will be different. By increasing or decreasing the intensity of the glow, you can create a variety of color shades. Thanks to this principle of operation of the plasma panel, it is possible to obtain high quality images without color and geometric distortions. The weak point is the relatively low contrast. This is due to the fact that the cells must be constantly supplied with low voltage current. Otherwise, the response time of the pixels (their lighting and fading) will be increased, which is unacceptable.

Now about the disadvantages.

The front electrode should be as transparent as possible. Indium tin oxide is used for this purpose because it is conductive and transparent. Unfortunately, plasma panels can be so large and the oxide layer so thin that when large currents flow across the resistance of the conductors there will be a voltage drop that will greatly reduce and distort the signals. Therefore, it is necessary to add intermediate connecting conductors made of chromium - it conducts current much better, but, unfortunately, is opaque. Plasma is afraid of not very delicate transportation. Electricity consumption is quite significant, although in recent generations it has been possible to significantly reduce it, at the same time eliminating noisy cooling fans.

"In my house PLASMA", - doesn't it, it sounds beautiful, by this we mean something very large and beautiful. Now almost all flat-panel TVs, even small ones, are teased with “plasma”. Agree, the word “plasma” sounds much cooler than LCD or LCD, LED ( some incomprehensible set of letters), this explains the subconscious craving for something such a huge and bewitchingly incomprehensible word plasma. And indeed, when you see such a plasma panel in front of you:

then you stand in front of her and don’t understand why she’s not at my house yet? Well, let's still figure out what a plasma panel is and how it works. Those who didn’t snore very much in physics lessons remember that a substance (water, for example, or metal...) can be in three states: solid (ice), liquid (water) or gaseous (steam), so plasma - this is the fourth state of matter. It is an ionized gas (a gas in which there are a lot of charged particles, like air after a thunderstorm, only much stronger)

If you run a lot of gas (neutral) electrons(they have a negative charge "-"), they will collide with gas atoms and knock out other electrons from them. Atom, having lost electrons, becomes ion(has a positive charge "+"). When an electric current passes through the resulting plasma, the negatively and positively charged particles are attracted to each other, the collisions "exciting" the gas atoms in the plasma, causing them to release energy in the form photons.

IN plasma panels mainly inert gases are used - neon And xenon. In a state of "excitement" they emit light in ultraviolet range invisible to the human eye, however, it can be used to release photons in the visible spectrum

A patent for the invention of a “plasma panel”, although it would be more correct to say “plasma display”, was issued in 1964 in the names of three people: Donald Bitzer, Slottov's wife And Robert Wilson. The first plasma display consisted of just one pixel(!!!), naturally, it was impossible to get any image from it other than a dot; the principle itself was important here. Less than ten years had passed since acceptable results were achieved, in 1971 year for the company Owens-Illinois the license for the production of displays was sold Digivue.

IN 1983 year, the University of Illinois earned no less than a million dollars for selling a plasma license to the company IBM- the strongest player, at that time, in the area computer technology. In front of you is a model 1981 of the year " PLATO V", with a monochromatic orange display:

Everything would be fine, but only LCD displays, which appeared in the early 90s, began to confidently displace “plasma” from the market. Unfortunately, creating small pixels (like LCD) was not so easy, and the brightness and contrast left much to be desired

Nobody knows what would have happened if the company had not taken up plasma panel technology." Matsushita"now known as" Panasonic". IN 1999 year, a promising 60-inch prototype was finally created with remarkable brightness and contrast, superior to their “liquid crystal” counterparts. This is what a plasma TV looks like without back cover:

Let's get a look, how does a plasma panel work? and how it works. In plasma panels xenon And neon contained in hundreds of small microchambers located between two glasses. On both sides, between the glasses and microchambers, there are two long electrode. Control electrodes located under the micro-chambers, along the rear glass. Transparent scanning electrodes, surrounded by a layer of dielectric and covered with a protective layer of magnesium oxide, are located above the microchambers, along the front glass

The electrodes are arranged crosswise across the entire width of the screen. The scanning electrodes are located horizontally, and the control electrodes are located vertically. As you can see in the diagram below, the vertical and horizontal electrodes form a rectangular grid. To ionize gas in a specific microchamber, the processor charges the electrodes directly at the intersection with this microchamber. Thousands of similar processes occur in a fraction of a second, charging each microchamber in turn.

When the intersecting electrodes are charged (one negatively and the other positively), the gas in the microchamber passes through electrical discharge. As mentioned earlier, this discharge causes charged particles to move, causing the gas atoms to emit ultraviolet photons, which, in turn, make them glow phosphorus coating microcameras, knocking out photons from the main ones visible colors.

Each pixel of a plasma panel consists of three microchambers (subpixels): red, green and blue (as in CRT TVs), the smaller the size of the pixels in the display, the clearer the image.

Plasma displays are different good brightness, clarity and beautiful color rendition. Unlike LCD and LED (liquid crystal displays), which work with backlighting, the plasma shines itself, providing beautiful and deep blacks and excellent image contrast from almost any viewing angle. Digital slowdowns and glitches are almost invisible on it, however, the pixel size is slightly larger than that of an LCD, so the size of a plasma panel (usually) starts from 32 inches

To the disadvantages Plasma can be attributed to its considerable cost and high energy consumption. If you have small children at home, please note that one hit with the ball or another toy may be enough for the entire plasma panel went to the landfill(there is no 5-10 centimeter glass in front of the screen, as in picture tubes)

FAQ: Do pixels burn out on plasma? And radioactive radiation? Ultraviolet light is indeed dangerous, but thanks to the front protective glass, the magnitude of its danger is zero. Have you tried sunbathing behind glass? It’s the same here, glass does not transmit ultraviolet rays, so there is absolutely nothing to fear. Pixel burn-in- although many claim that it does not exist, but it is, so you don’t need to leave a motionless picture on the screen for a long time (a long time means several days, nothing will happen in an hour or two)

Remember that a TV with a plasma panel, no matter how good it is, can also fail, and its repair is a very complex and expensive thing. When buying such a beauty as in the picture, be prepared for its appropriate maintenance.