Plasma displays and televisions (PDP). Plasma display - what is it?

Phil Connor
November 2002

Which is better: plasma panel or LCD TV?

It depends on many factors. The topic of discussion of the two technologies, which process and display video or computer input signal in completely different ways, is complex and rich in numerous details. Both technologies are progressing rapidly, and their production costs and retail prices are falling at the same time. In the near future, there will inevitably be a clash between these technologies in the line of 40-inch (diagonal) monitors/TVs.

Some of the benefits of each technology are listed below; The relationship between these benefits and the buyers of each technology in different application areas is also explained:

1) SCREEN BURNING

For LCD, you can ignore the factors that lead to screen burn-in when displaying a static image. LCD (liquid crystal display) technology uses essentially a fluorescent back lamp, the light from which passes through a pixel matrix containing liquid crystal molecules and a polarized substrate to impart brightness and color to the form. The liquid crystal found in the LCD is actually used in a solid state.

In plasma technology, on the contrary, factors that lead to screen burn-in when displaying a static image should be taken into account. Static images will begin to "burn in" the displayed image after just a short period of time - in some cases, after about 15 minutes. Although "burn-in" can usually be "removed" by displaying gray or alternating solid-color fields on the entire screen, it is nevertheless a significant factor hindering the development of plasma technology.

Advantage: LCD

For applications such as flight information displays at airports, static displays in retail stores, or permanent information displays, an LCD monitor is the best option.

2) CONTRAST

Plasma technology has made significant advances in the development of high contrast images. Panasonic claims their plasma displays have a contrast ratio of 3000:1. Plasma technology simply blocks power supply (through complex internal algorithms) to certain pixels in order to produce dark or black pixels. This technique does indeed produce dark black colors, although sometimes at the expense of developing midtones.

In LCD technology, on the contrary, you need to increase the energy supply to make the pixels darker. The higher the voltage applied to a pixel, the darker the LCD pixel. Despite the improvements that LCD technology has made in terms of contrast and black levels, even the best LCD technology manufacturers, such as Sharp, can only provide contrast ratios between 500:1 and 700:1.

For watching DVD movies, where there are usually a lot of very light and very dark scenes, and in computer games with a characteristic abundance of dark scenes, the plasma panel has a clear advantage.

3) DURABILITY

LCD manufacturers claim that the durability of their monitors/TVs ranges from 50,000 to 75,000 hours. An LCD monitor can last as long as the rear lamp (which is actually replaceable) because the light from it, exposed to the liquid crystal prism, provides brightness and color. The prism is a substrate and therefore does not actually burn anything away.

On the other hand, in plasma technology, an electrical pulse is applied to each pixel, which excites the inert gases - argon, neon and xenon (phosphors), necessary to provide color and brightness. When the electrons excite the phosphor, the oxygen atoms are scattered. Plasma manufacturers estimate the durability of the phosphors and, therefore, the panels themselves at 25,000 – 30,000 hours. Phosphors cannot be replaced. There is no such thing as pumping new gases into a plasma display.

Advantage: LCD, twice or more.

In industrial/commercial applications (such as signage displays where displays must operate 24/7), where image quality requirements are typically not too demanding, LCD will be the best option for long-term use.

4) COLOR SATURATION

Color is more accurately reproduced in plasma panels because all the information needed to reproduce any shade in the spectrum is contained in each cell. Each pixel contains blue, green and red elements for accurate color reproduction. The saturation achieved by the plasma panel's pixel design produces, in my opinion, the most vibrant colors of any display type. The color coordinates in the color space in good plasma panels are much more accurate than in LCD.

In LCD, due to the physical conditions of the passage of waves through long thin liquid crystal molecules, it is more difficult to achieve reference accuracy and vivid color rendering. Color information takes advantage of the smaller pixel size of most LCD TVs. However, with the same pixel size, the color will not be as expressive as with plasma panels.

Plasma technology is superior to LCD when displaying video, especially in dynamic scenes. LCD is preferred for displaying static computer images, not only because of burn-in, but because it also provides excellent, uniform colors.

5) ALTITUDE ABOVE SEA LEVEL

As mentioned above, LCD uses backlight technology in combination with liquid crystal molecules. In principle, there is nothing that would prevent this monitor from being placed at high altitudes, and there are no real restrictions. This explains the use of LCD screens as the main overview screen for displaying video information about flights.

Since the plasma screen cell in plasma panels is actually a glass shell filled with an inert gas, the rarefied air leads to an increase in gas pressure inside this shell and increases the power required for normal cooling of the plasma panel, resulting in a characteristic hum (buzzing) and excessive noticeable noise from the fan. These problems occur at an altitude of approximately 2,000 meters.

Advantage: LCD

At Denver altitude and above, I would use LCD monitors for any application.

6) VIEWING ANGLE

Manufacturers of plasma monitors have always claimed that their products have a viewing angle of 160° - in fact, this is so. LCD has made significant strides in increasing viewing angles. In new generation LCD monitors from Sharp and NEC, the LCD base material has been significantly improved; The dynamic range is also expanded. But despite these advances, when viewing a monitor/TV at high angles, a noticeable difference between the two technologies still remains.

Advantage: plasma panel

Each cell of the plasma panel is an independent light source, which allows you to achieve excellent brightness of each pixel. The absence of a backlight device (like LCD) is also good in terms of viewing angle.

7) USE WITH A COMPUTER

LCD displays static computer images efficiently, without flickering or screen burn-in.

It is more difficult for a plasma panel to process static images from a computer. While their display looks satisfactory, screen burn-in is an issue; presents the difficulty and staggering effect found in panels with lower resolution when displaying static text (Power Point). Video images from the computer are of high quality, but some flickering is possible, depending on both the factory quality of the panel and the displayed resolution. The plasma panel, of course, still wins in terms of viewing angle.

Advantage: LCD, except for large viewing angles.

8) PLAYING VIDEO

Here, plasma panels take the lead, thanks to their excellent quality when displaying scenes with fast movement, high levels of brightness, contrast and color saturation.

Color trailing may be noticeable on LCDs during fast-moving video scenes because the technology is slower to process color changes. The reason for this is the light prisms, which must appear due to the influence of voltage that controls the deflection of the light beam. The higher the voltage applied to the crystal, the darker the image becomes in that part of the LCD panel. This is also why LCDs have lower contrast levels.

Advantage: plasma panel, with a large margin.

DVD or any streaming video, TV or HDTV - from any of these video sources, the plasma panel will display an unblurred, high-contrast (depending on the plasma), color-rich image. Despite significant advances in this area, LCD still suffers from some difficulties at relatively large screen sizes, although it looks excellent at smaller sizes.

9) PRODUCTION VOLUME AND COST

Although both technologies have difficulty creating large monitors, a large plasma panel has proven to be easier to make, with manufacturers already producing plasma panels with a diagonal of more than 60 inches. Although such monitors are still expensive, they have demonstrated their effectiveness and reliability. A large LCD base for an LCD TV is difficult to produce without defective pixels. At the moment, the largest LCD screen is a 40-inch commercial version from NEC. Sharp has previously expanded its line of LCD monitors from 20 to 22 to 30 inches, and is now introducing a new 37-inch widescreen panel to the market.

Advantage: plasma panel.

Although the cost and product prices of both technologies are decreasing (except for the prices of large plasma panels), the plasma panel still has a lower production cost and therefore has a price advantage. 50-inch plasma panels are extremely popular and are quickly gaining market share from the previously dominant 42-inch panels. This trend for plasma panels, which have higher production yields and therefore lower costs, will likely continue for at least 2 years.

10) VOLTAGE REQUIREMENTS

Because LCDs use a fluorescent backlight to produce light, the technology has much lower voltage requirements than plasma panels. On the other hand, when using a plasma panel, a necessary (difficult to fulfill) condition is the supply of power to hundreds of thousands of transparent electrodes, which excite the glow of the phosphor cells.

The main problem with the development of LCD technology for the desktop sector seems to be the size of the monitor, which affects its cost. However, despite this, LCD monitors have today become the undisputed leaders in the display market. However, there are other technologies being created and developed by different manufacturers, and some of these technologies are called PDP (Plasma Display Panels), or simply "plasma", and FED (Field Emission Display).

Plasma monitors

The development of plasma displays, which began back 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 effect of the glow of an inert gas under the influence of electricity is used. Neon lamps work using approximately the same technology. Note that the powerful magnets that are part of the dynamic sound emitters located next to the screen do not affect the image in any way, since in plasma devices, as in LCDs, there is no such thing as an electron beam, and at the same time all the elements of a CRT, on which are 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 adjacent cells and selecting a gas mixture that, when discharged, emitted ultraviolet radiation invisible to the eye, which excited the phosphors and created a visible color image.

However, traditional plasma screens on panels with a direct current discharge also have a number of disadvantages caused by the physics of the processes occurring in this type of discharge 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 display boards to display alphanumeric and graphical information. The problem is fundamentally solved at the physical level by applying a dielectric protective coating to the discharge electrodes.

Modern plasma displays used as computer monitors 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). Each subpixel is individually controlled electronically and produces more than 16 million different colors. In modern models, each individual red, blue or green dot can glow at one of 256 brightness levels, which when multiplied gives about 16.7 million shades of a combined color pixel. In computer jargon, this color depth is called “True Color” and is considered quite sufficient to convey a photographic quality image.

Speaking about the functionality of a plasma monitor, we can say that the screen has the following functional advantages:

• Wide viewing angle both horizontally and vertically (160° degrees or more).

• Very fast response time (4 µs per line).

• High color purity, equivalent to the purity of the three primary colors of a CRT.

• Ease of production of large-format panels, unattainable with the thin-film process.

• Low thickness (the gas discharge panel is about one centimeter or less thick, and the control electronics add a few more centimeters).

• Compact (depth does not exceed 10 - 15 cm) and light with fairly large screen sizes (40 - 50 inches).

• High refresh rate (about five times better than an LCD panel).

• No flickering or blurring of moving objects that occurs during digital processing.

• High brightness, contrast and clarity without geometric image distortion.

• Wide temperature range.

• 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.

• Absence of X-rays and other radiation harmful to health, since high voltages are not used.

• Immunity to magnetic fields.

• No need to adjust the image.

• Mechanical strength.

• Wide temperature range.

• The short response time allows them to be used for displaying video and television signals.

• Higher reliability.

All this makes plasma displays very attractive for use. However, the disadvantages include the limited resolution of most existing plasma monitors, which does not exceed 640x480 pixels. The exception is the PDP-V501MX and 502MX models 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 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, which is why we don't see plasma panels in, say, laptop computers. This assumption is supported by another fact: the level of energy consumption of such monitors 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.

On this page we will talk about topics such as: Output devices, , Plasma monitors, Cathode ray tube monitors.

Monitor (display) a device for visually displaying information, designed for screen output text and graphic information.

Characterized by monitor diagonal size, resolution, grain size, maximum frame refresh rate, connection type.

Monitor types:

• Colored and monochrome.
• Various sizes (from 14 inches).
• With various grains.
• Liquid crystal and cathode ray tube.

Monitor operates under the control of a special hardware device - a video adapter (video controller, video card), which provides two possible modes - text and graphic.

In text mode screen is divided (most often) into 25 lines of 80 positions in each line (2000 positions in total). Each position (familiarity) can contain any of the symbols of the code table - an uppercase or lowercase letter of the Latin or Russian alphabet, a service sign (“+”, “-”, “.”, etc.), a pseudographic symbol, as well as a graphic image almost every control character. For each familiarity on the screen, the program working with the screen reports only two bytes to the video controller - a byte with the character code and a byte with the character color and background color code. And the video controller generates an image on screen.

In graphic mode, the image is formed in the same way as in screen TV - a mosaic, a collection of dots, each of which is painted in one color or another. On screen in graphical mode you can display texts, graphs, pictures, etc. And when outputting tests, you can use different fonts, any sizes, fonts, any sizes, colors, letter placement. In graphical mode screen monitor is essentially a raster made up of pixels.

Note

The minimum element of an image on the screen (dot) is called a pixel - from the English “picture element”...

The number of horizontal and vertical points that monitor able to reproduce clearly and separately is called the dilution ability of the monitor. The expression "rarefaction" monitor 1024x768" means that monitor can output 1024 horizontal lines with 768 dots per line.

There are two main types monitor: liquid crystal and with cathode ray tube. Less common are plasma monitors And touch screen monitors.

Cathode ray tube monitors.

Screen image cathode ray tube monitor is created by a beam of electrons emitted by an electron gun and the principle of their operation is similar to the principle of operation of a TV. This beam (a beam of electrons) is accelerated by high electrical voltage and falls on the inner surface of the screen, coated with a phosphor composition that glows under its interaction.

The phosphor is applied in the form of sets of dots of three primary colors - red (Red), green (Green) and blue (Blue). These colors are called primary because their combinations (in various proportions) can represent any color in the spectrum. The color model in which the image on the monitor screen is constructed is called RGB. The sets of phosphor dots are arranged in triangular triads. The triad forms a pixel - a point from which an image is formed.

The distance between the centers of pixels is called the dot pitch monitor. This distance significantly affects the clarity of the image. The smaller the step, the higher the clarity. Usually in colored monitors the pitch (diagonally) is 0.27-0.28 mm. With this step, the human eye perceives the points of the triad as one point of a “complex” color.

On the opposite side tubes There are three (according to the number of primary colors) electron guns. All three guns are “aimed” at the same pixel, but each of them emits a stream of electrons towards “its own” phosphor point.

In order for electrons to reach the screen unhindered, air is pumped out of the tube, and a high electrical voltage is created between the guns and the screen, accelerating the electrons.

In front of the screen, in the path of the electrons, a mask is placed - a thin metal plate with a large number of holes located opposite the phosphor points. The mask ensures that electron beams hit only the phosphor points of the corresponding color. The magnitude of the electronic current of the guns and, consequently, the brightness of the pixels is controlled by the signal coming from the video adapter.

A deflection system is placed on the part of the flask where the electron guns are located. monitor, which causes the electron beam to run through all the pixels one by one, line by line, from top to bottom, then return to the beginning of the top line, etc. The number of lines displayed per second is called the horizontal scan rate. And the frequency with which the image frames change is called the frame rate.

Note

The latter should not be lower than 60 Hz, otherwise the image will flicker...

LCD monitors.

LCD monitors (LCD) have less weight, geometric volume, consume two orders of magnitude less energy, do not emit electromagnetic waves that affect human health, but are more expensive than monitors with cathode ray tube.

Liquid crystals- this is a special state of some organic substances, in which they have fluidity and the ability to form spatial structures similar to crystalline.

Liquid crystals can change their structure and light-optical properties under the influence of electrical voltage. By changing the orientation of groups of crystals using an electric field and using the entered liquid crystal a solution of substances capable of emitting light under the influence of an electric field, it is possible to create high-quality images that convey more than 15 million colors.

Majority LCD monitors uses a thin film of liquid crystals, placed between two glass plates. The charges are transmitted through the so-called passive matrix - a grid of invisible threads, horizontal and vertical, creating an image point at the intersection of the threads (somewhat blurred due to the fact that the charges penetrate into neighboring areas of the liquid).

Plasma monitors.

Job plasma monitors very similar to the work of neon lamps, which are made in the form of a tube filled with an inert gas of low pressure. A pair of electrodes is placed inside the tube, between which an electric discharge is ignited and a glow occurs. Plasma screens are created by filling the space between two glass surfaces with an inert gas, such as argon or neon.

Small transparent electrodes are then placed on the glass surface and high frequency voltages are applied to them. Under the influence of this voltage, an electric discharge occurs in the gas region adjacent to the electrode. The gas discharge plasma emits light in the ultraviolet range, which causes phosphor particles to glow in the range visible to humans. In fact, every pixel on the screen works like a regular fluorescent lamp.

High brightness, contrast and no jitter are the big advantages of such monitors. In addition, the angle relative to that at which a normal image can be seen on plasma monitors– 160° compared to 145° as in the case of LCD monitors. With great dignity plasma monitors is their service life. The average service life without loss of image quality is 30,000 hours. This is three times more than usual cathode ray tube. The only thing that limits their widespread use is cost.

Type of monitor – with touch screen. Here, communication with the computer is carried out by touching a certain place on the sensitive screen with your finger. This selects the desired mode from the menu shown on the screen monitor.

I decided to look into such a glamorous topic as a plasma display.

Many people are tormented by the question: “What is a plasma display and how cool is it, or better yet, how convenient is it?” We will analyze this topic piece by piece and find out the whole point!

Name

Why did we start with the title? That's right, there are at least 3 different and frequently used options for this device (Display, panel, screen), which need to be dealt with first.
Panel is the most sonorous and commonly used name for this type of screen. The expression “I have a plasma panel at home” has become something attractive and powerful, because in our subconscious we imagine something large, high-tech with a rich picture. The irony is that the word panel is incorrect to use in relation to, monitor, etc. Stylistically correct word, grammatically incorrect.
Display is the second most used, correct and grammatical. Because the patent registered by the three men who were the first to bring this technology to life contained precisely the word Display.
The screen is fine, why not. Synonym for display.

Let's compare

We will present the data in comparison with, this is obvious. Yes, they have their own benefits, but they are not used in the segment where plasma and LCD are.

Advantages

• Show off.
• Realism of the image (debatable).
• Initially, deep color reproduction, but this pales against the background of new LED and OLED backlights, which already convey better colors.

Flaws

• The price of devices with such screens and the presence of functions is higher than their counterparts with LCD.
• Higher power consumption.
• Due to their structure, pixels quickly burn out when a static picture is turned on for a long time. As a result, it can only be used for viewing dynamic scenes.
• Large pixels, resulting in relatively small screens with poor resolution.
• The smallest width of the displays is greater than the smallest width of the LCD.

Design

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 sub-pixel has the following dimensions: 200 µm x 200 µm 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, helium and/or argon, or, more often, mixtures thereof) are used with the addition of mercury.

Operating principle

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 (+75 V) is supplied to the addressing bus, and a negative pulse (-75 V) is supplied to the scanning bus. On the backlight bus, the voltage is set to +150 V.
3. illumination, 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 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.

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.

Conclusion: If you are a terrible major and are not even going to look at this TV. Buy the largest display size available in the store and boldly rock your home theater, then say that you have all this at home and invite a bunch of friends who won’t look there either. True, my dear reader, because of your wallet, you should stick to the voice of reason and buy a TV or monitor only with an LCD screen.

A plasma panel is a matrix of gas-filled cells enclosed between two parallel glass plates, inside which transparent electrodes are located, forming scanning, illumination and addressing buses, respectively. 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 sub-pixel of the plasma panel has the following dimensions: 200 µm x 200 µm 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 gas - neon or xenon (less commonly, He and/or Ar, or, more often, their mixtures are used).

The phosphors in the pixels of the plasma panel have the following composition:

· Green: Zn 2 SiO 4: Mn 2+ / BaAl 12 O 19: Mn 2+ ; + / YBO 3: Tb / (Y, Gd) BO 3: Eu

Red: Y 2 O 3: Eu 3+ / Y 0.65 Gd 0.35 BO 3: Eu 3+

Blue: BaMgAl 10 O 17: Eu 2+

The current problem of addressing millions of pixels is solved by arranging the front pair of tracks as rows (the scan and backlight buses) and each rear track as columns (the address bus). The internal electronics of plasma screens automatically select the desired 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 does not allow the human eye to notice screen flickering.

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 (about the same way as neon lamps work).

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 having 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 (+75 V) is supplied to the addressing bus, and a negative pulse (-75 V) is supplied to the scanning bus. On the backlight bus, the voltage is set to +150 V.

3. Illumination, 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 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, you can 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.

Figure 1. Cell design

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, passing through the front glass plate, enters the viewer's eye.

The operation of plasma monitors is very similar to the operation of neon lamps, which are made in the form of a tube filled with an inert gas of low pressure. A pair of electrodes is placed inside the tube, between which an electric discharge is ignited and a glow occurs. Plasma screens are created by filling the space between two glass surfaces with an inert gas, such as argon or neon. Small transparent electrodes are then placed on the glass surface and high frequency voltage is applied to them. Under the influence of this voltage, an electric discharge occurs in the gas region adjacent to the electrode. The gas discharge plasma emits light in the ultraviolet range, which causes phosphor particles to glow in the range visible to humans.

In fact, every pixel on the screen works like a regular fluorescent lamp (in other words, a fluorescent lamp). The basic principle of operation of a plasma panel is a controlled cold discharge of rarefied gas (xenon or neon) in an ionized state (cold plasma). The working element (pixel), which forms a separate point in the image, is a group of three subpixels responsible for the three primary colors, respectively. Each subpixel is a separate microchamber, on the walls of which there is a fluorescent substance of one of the primary colors. The pixels are located at the intersection points of transparent control chromium-copper-chromium electrodes, forming a rectangular grid.

Figure 2. Structure in a cell

In order to “light up” a pixel, approximately the following happens. A high rectangular control alternating voltage is supplied to the supply and control electrodes, orthogonal to each other, at the intersection point of which the desired pixel is located. The gas in the cell gives up most of its valence electrons and turns into a plasma state. Ions and electrons are alternately collected at the electrodes on opposite sides of the chamber, depending on the phase of the control voltage. To “ignite” a pulse is applied to the scanning electrode, the potentials of the same name are added, and the electrostatic field vector doubles its value. A discharge occurs - some of the charged ions give off energy in the form of radiation of light quanta in the ultraviolet range (depending on the gas). In turn, the fluorescent coating, being in the discharge zone, begins to emit light in the visible range, which is perceived by the observer. 97% of the ultraviolet component of radiation, harmful to the eyes, is absorbed by the outer glass. The brightness of the phosphor is determined by the value of the control voltage.

Figure 3. Cell design of an AC color gas discharge panel

High brightness (up to 650 cd/m2) and contrast (up to 3000:

1) along with the absence of jitter, are the great advantages of such monitors (For comparison: a professional CRT monitor has a brightness of approximately 350 cd/m2, and a TV has a brightness of 200 to 270 cd/m2 with a contrast ratio of 150: 1 to 200:

1). High image clarity is maintained across the entire working surface of the screen. In addition, the angle relative to the normal at which a normal image can be seen on plasma monitors is significantly greater than that of LCD monitors. In addition, plasma panels do not create magnetic fields (which guarantees their harmlessness to health), do not suffer from vibration like CRT monitors, and their short regeneration time allows them to be used for displaying video and television signals. The absence of distortion and problems of electron beam convergence and focusing is inherent in all flat panel displays. It should also be noted that PDP monitors are resistant to electromagnetic fields, which allows them to be used in industrial environments - even a powerful magnet placed next to such a display will not affect the image quality in any way. At home, you can put any speakers on the monitor without fear of color spots appearing on the screen.

The main disadvantages of this type of monitor are the rather high power consumption, which increases with increasing monitor diagonal, and low resolution due to the large size of the image element. In addition, the properties of the phosphor elements quickly deteriorate, and the screen becomes less bright. Therefore, the service life of plasma monitors is limited to 10,000 hours (this is about 5 years for office use). Due to these limitations, such monitors are currently used only for conferences, presentations, information boards, that is, where large screen sizes are required to display information.