The plasma panel is an array of gas-filled cells enclosed between two parallel glass plates, inside of which transparent electrodes are located, which form, respectively, the scanning, illumination and addressing lines. The discharge in gas flows between the discharge electrodes (scan and backlight) on the front side of the screen and the addressing electrode on the back side.
Design features:
· A sub-pixel of a plasma panel has the following dimensions: 200 µm × 200 µm × 100 µm;
· The front electrode is made of indium and tin oxide, since it is conductive and as transparent as possible.
· When high currents flow through a rather large plasma screen, due to the resistance of the conductors, a significant voltage drop occurs, leading to signal distortions, and therefore intermediate conductors made of chromium are added, despite its opacity;
· To create plasma, the cells are usually filled with gas - neon or xenon (less often He and / or Ar is used, or, more often, their mixed mixture).
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 existing problem in addressing millions of pixels is solved by arranging a pair of front tracks as rows (scan and backlight bus), and each back track as columns (address bus). The internal electronics of plasma screens automatically selects the correct pixels. This operation is faster than beam scanning on CRT monitors. In the latest PDP models, the screen is refreshed at frequencies of 400-600 Hz, which prevents the human eye from noticing screen flickers.
The principle of operation of the monitor is based on plasma technology: the effect of glow of an inert gas under the influence of electricity is used (in much the same way as neon lamps work).
Plasma panel operation consists of three stages:
1. Initialization, during which there is an ordering of the position of the charges of the medium and its preparation 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 gaseous medium is ordered, at the second stage there is a discharge in the gas, and at the third stage, the ordering is completed.
2. Addressing, during which the pixel is prepared for highlighting. A positive pulse (+75 V) is applied to the address bus, and a negative pulse (-75 V) to the scan bus. The backlight bus is set to +150 V.
3. Backlight, during which a positive pulse is applied to the scanning bus and a negative pulse equal to 190 V to the backlight bus. The sum of the ion potentials on each bus and additional pulses leads to an excess of the threshold potential and a discharge in the gaseous medium. After the discharge, the ions are redistributed at the scanning and illumination buses. A change in the polarity of the pulses leads to a repeated discharge in the plasma. Thus, by changing the polarity of the pulses, a multiple discharge of the cell is provided.
One cycle "initialization - addressing - backlighting" forms the formation of 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.
Figure 1. Design in cells
Thus, when a 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.
Plasma monitors work very much like neon lamps, which are made in the form of a tube filled with a low pressure inert gas. A pair of electrodes is placed inside the tube, between which an electric discharge is ignited and a glow arises. Plasma screens are created by filling the space between two glass surfaces with an inert gas such as argon or neon. Then small transparent electrodes are placed on the glass surface, to which high-frequency voltage is applied. Under the action of this voltage, an electric discharge arises in the gas region adjacent to the electrode. Gas discharge plasma emits light in the ultraviolet range, which causes the phosphor particles to glow in the range visible to humans.
In fact, every pixel on the screen acts 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 a rarefied gas (xenon or neon) in an ionized state (cold plasma). The working element (pixel) that 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 microcamera, on the walls of which there is a fluorescent substance of one of the primary colors. The pixels are located at the intersection of the transparent control chromium-copper-chromium electrodes, forming a rectangular grid.
Figure 2. Design in a cell
In order to "light up" a pixel, something like the following happens. A high control AC voltage of a rectangular shape 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 transforms into a plasma state. Ions and electrons are alternately collected at the electrodes, on different sides of the chamber, depending on the phase of the control voltage. For "ignition" a pulse is applied to the scanning electrode, the potentials of the same name are added, and the vector of the electrostatic field doubles its value. A discharge occurs - some of the charged ions give up energy in the form of emission 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 UV radiation harmful to the eyes is absorbed by the outer glass. The luminescence brightness of the phosphor is determined by the value of the control voltage.
Figure 3. Device of a cell of a color discharge panel of alternating current
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: for a professional CRT monitor, the brightness is approximately 350 cd / m2, and for a TV - from 200 to 270 cd / m2 with a contrast ratio of 150: 1 to 200:
one). The high definition of the image is maintained over the entire working surface of the screen. In addition, the angle with respect to the normal at which to see a normal image 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 TV signals. The lack of distortion and problems of converging electron beams and their focusing is inherent in all flat panel displays. It should be noted that PDP monitors are resistant to electromagnetic fields, which allows them to be used in industrial conditions - even a powerful magnet placed next to such a display will not affect the image quality in any way. At home, however, you can put any speakers on the monitor without fear of color spots on the screen.
The main disadvantages of this type of monitors are rather high power consumption, which increases with increasing diagonal of the monitor and low resolution due to the large size of the image element. In addition, the properties of the phosphor elements deteriorate rapidly 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 used so far only for conferences, presentations, information boards, that is, where large screen sizes are required to display information.
In a cathode-ray tube monitor, image dots are displayed using a beam (a stream of electrons) that causes the phosphor-coated surface of the screen to glow. The beam runs around the screen line by line, from left to right and from top to bottom. The full cycle of displaying a picture is called a "frame". The faster the monitor displays and redraws frames, the more stable the picture seems, the less noticeable flickering and less tired our eyes.
CRT monitor device. 1 -Electronic cannons. 2 - Electron beams. 3 - Focusing coil. 4 - Deflecting coils. 5 - Anode. 6 - Mask, due to which the red ray hits the red phosphor, etc. 7 - Red, green and blue grains of the phosphor. 8 - Mask and grains of phosphor (enlarged).
LCD
Liquid crystal displays were developed in 1963 at RCA's David Sarnoff Research Center in Princeton, NJ.
Device
Structurally, the display consists of an LCD matrix (a glass plate, between the layers of which liquid crystals are located), light sources for backlighting, a contact harness and a frame (case), usually plastic, with a metal frame of rigidity. Each pixel of an LCD matrix consists of a layer of molecules between two transparent electrodes, and two polarizing filters, the polarization planes of which are (as a rule) perpendicular. If there were no liquid crystals, then the light transmitted by the first filter would be almost completely blocked by the second filter. The surface of the electrodes in contact with liquid crystals is specially treated for the initial orientation of the molecules in one direction. In a TN matrix, these directions are mutually perpendicular; therefore, in the absence of stress, the molecules are arranged in a helical structure. This structure refracts light in such a way that before the second filter the plane of its polarization is rotated and light passes through it without loss. Except for the absorption of half of the unpolarized light by the first filter, the cell can be considered transparent. If a voltage is applied to the electrodes, then the molecules tend to line up in the direction of the electric field, which distorts the helical structure. In this case, the elastic forces counteract this, and when the voltage is turned off, the molecules return to their original position. With a sufficient field strength, almost all molecules become parallel, which leads to the opacity of the structure. By varying the voltage, you can control the degree of transparency. If a constant voltage is applied for a long time, the liquid crystal structure may degrade due to ion migration. To solve this problem, an alternating current or a change in the polarity of the field is used with each addressing of the cell (since a change in transparency occurs when the current is turned on, regardless of its polarity). In the entire matrix, each of the cells can be controlled individually, but with an increase in their number, this becomes difficult, since the number of required electrodes increases. Therefore, row and column addressing is used almost everywhere. Light passing through the cells can be natural - reflected from the substrate (in LCD displays without backlighting). But more often an artificial light source is used, in addition to independence from external lighting, this also stabilizes the properties of the resulting image. Thus, a full-fledged LCD monitor consists of high-precision electronics that process the input video signal, an LCD matrix, a backlight module, a power supply and a housing with control elements. It is the combination of these components that determines the properties of the monitor as a whole, although some characteristics are more important than others.
Backlight
By themselves, liquid crystals do not glow. In order for the image on the liquid crystal display to be visible, a light source is needed. The source can be external (for example, the sun) or built-in (backlight). Typically, built-in backlight lamps are located behind the liquid crystal layer and shine through it (although side illumination is also found, for example, in watches).
- External lighting
- Incandescent lighting In the past, some monochrome LCD wristwatches used a subminiature incandescent lamp. But due to the high energy consumption, incandescent lamps are disadvantageous. In addition, they are not suitable for use, for example, in televisions, as they generate a lot of heat (overheating is harmful for liquid crystals) and often burn out.
- Illumination by gas-discharge ("plasma") lamps During the first decade of the 21st century, the vast majority of LCD displays were backlit from one or more gas discharge lamps (most often with a cold cathode - CCFL). In these lamps, the light source is a plasma generated by an electrical discharge through a gas. Such displays should not be confused with plasma displays, in which each pixel itself glows and is a miniature gas discharge lamp.
- LED (LED) backlight On the border of the first and second decades of the XXI century, LCD displays with backlighting from one or a small number of light-emitting diodes (LEDs) have become widespread. Such LCDs (often called LED displays in the trade) should not be confused with real LED displays, in which each pixel itself glows and is a miniature LED.
Monochrome displays of wristwatches and mobile phones use external lighting (from the sun, room lamps, etc.) most of the time. There is usually a specular or matte reflective layer behind the liquid crystal pixel layer. For use in the dark, these displays are equipped with side illumination. There are also transflective displays in which the reflective (specular) layer is translucent and the backlights are located behind it.
Advantages and disadvantages
Currently, LCD monitors are the main, rapidly developing direction in monitor technology. Their advantages include: small size and weight in comparison with CRT. LCD monitors, unlike CRTs, have no visible flicker, beam focusing defects, magnetic field interference, and problems with image geometry and clarity. The power consumption of LCD monitors, depending on the model, settings and the displayed image, can either coincide with the consumption of CRT and plasma screens of comparable sizes, or be significant - up to five times - lower. The power consumption of LCD monitors is 95% determined by the power of the backlight lamps or the LED backlight (backlight) of the LCD matrix. Many 2007 monitors use pulse width modulation of backlight lamps with a frequency of 150 to 400 or more hertz to adjust the brightness of the screen by the user. On the other hand, LCD monitors also have some disadvantages, which are often difficult to eliminate in principle, for example:
- Unlike CRTs, they can display a clear image in only one ("native") resolution. The rest are achieved by lossy interpolation. And too low resolutions (for example 320 * 200) cannot be displayed at all on many monitors.
- Many of the LCD monitors have relatively low contrast and black depth. Increasing the actual contrast is often associated with simply increasing the brightness of the backlight to an uncomfortable level. The widely used glossy coating of the matrix affects only the subjective contrast in ambient light conditions.
- Due to strict requirements for constant matrix thickness, there is a problem of uneven uniform color (uneven illumination) - on some monitors there is an unrecoverable unevenness in brightness transmission (bands in gradients) associated with the use of linear mercury lamp units.
- The actual picture change rate also remains lower than that of CRT and plasma displays. Overdrive technology only partially solves the speed problem.
- The dependence of the contrast on the viewing angle is still a significant disadvantage of the technology.
- Mass-produced LCD monitors are poorly protected from damage. The matrix, which is not protected by glass, is especially sensitive. When pressed firmly, irreversible degradation is possible. There is also the problem of defective pixels. The maximum permissible number of defective pixels, depending on the screen size, is determined in the international standard ISO 13406-2 (in Russia - GOST R 52324-2005). The standard defines 4 quality classes for LCD monitors. The highest grade - 1, does not allow for defective pixels at all. The lowest is 4, allowing up to 262 defective pixels per million working.
- LCD pixels degrade, although the rate of degradation is the lowest of all display technologies, with the exception of laser displays that are not.
The plasma panel is an array of gas-filled cells enclosed between two parallel glass plates, inside of which are transparent electrodes that form scan, backlight and address lines. The discharge in gas flows between the discharge electrodes (scan and backlight) on the front side of the screen and the addressing electrode on the back side.
To create organic light-emitting diodes (OLED), thin-film multilayer structures are used, consisting of layers of several polymers. When a voltage positive with respect to the cathode is applied to the anode, the flow of electrons flows through the device from the cathode to the anode. Thus, the cathode donates electrons to the emission layer, and the anode picks up electrons from the conductive layer, or in other words, the anode donates holes to the conductive layer. The emission layer is negatively charged and the conductive layer is positive. Under the influence of electrostatic forces, electrons and holes move towards each other and recombine when they meet. This happens closer to the emission layer, because holes in organic semiconductors have a higher mobility than electrons. During recombination, a decrease in the energy of an electron occurs, which is accompanied by the emission (emission) of electromagnetic radiation in the region of visible light. Therefore, the layer is called emission. The device does not work when a negative voltage with respect to the cathode is applied to the anode. In this case, holes move to the anode, and electrons in the opposite direction to the cathode, and no recombination occurs. Indium oxide doped with tin is usually used as the anode material. It is transparent to visible light and has a high work function that facilitates the injection of holes into the polymer layer. Metals such as aluminum and calcium are often used for the manufacture of the cathode, since they have a low work function, which facilitates the injection of electrons into the polymer layer.
A projector is a light device that redistributes the light of a lamp with a concentration of the luminous flux on a surface of a small size or in a small volume. Projectors are mainly optical-mechanical or optical-digital devices that allow using a light source to project images of objects onto a surface located outside the device - a screen.
It is a multimedia projector that is used in tandem with a computer (the term “Digital projector” is also used.) A real-time video signal (analog or digital) is supplied to the input of the device. The device projects an image onto the screen. In this case, the presence of an audio channel is possible.
Speaking of projectors, it is worth mentioning the so-called pico projector. This is a small, pocket sized projector. It is often made in the form factor of a cell phone and has a similar size. The term "pico projector" can also mean a miniature projector built into a camera, mobile phone, PDA and other mobile equipment.
Anaglyph method(anaglyph means "relief" in Greek). In the early days of 3D cinema, only black and white 3D films were released. In each appropriately equipped cinema, two cinema projectors were used to display them. One was projecting the film through a red filter, the other was displaying slightly horizontally displaced film frames, passing them through a green filter. Visitors put on light cardboard glasses, in which, instead of glasses, pieces of red and green transparent film were installed, so that each eye saw only the desired part of the image, and the audience perceived the “volumetric” picture. However, both cinema projectors must be directed strictly at the screen and work absolutely synchronously. Otherwise, a split image is inevitable and, as a result, headaches instead of viewing pleasure - in viewers.
Shutter method. Optimal for watching color films. In contrast to the anaglyphic method, this method involves alternating display of images intended for the left and right eyes by the projector. Due to the fact that the interleaving of images is carried out at a high frequency - from 30 to 100 times per second - the brain builds a holistic spatial picture and the viewer sees a whole three-dimensional image on the screen. This method was formerly called NuVision, now it is more commonly referred to as XpanD.
Polarization method. In the field of cinema, this solution is called RealD. Its essence is that the projector alternately shows motion pictures in which the light waves have a different direction of polarization of the light flux. The special glasses required for viewing are equipped with filters that transmit only light waves polarized in a certain way. So both eyes receive images with different information, on the basis of which the brain forms a three-dimensional picture.
But the release of 3D-TVs working in tandem with glasses, several manufacturers announced at the international exhibition IFA 2009 at once. For example, Panasonic intends to release 3D TV models by mid-2010, just like Sony and Loewe, relying on the shutter method. JVC, Philips and Toshiba are also striving to climb the "3D podium", but they prefer the polarization method. LG and Samsung are developing their devices based on both technologies.
However, these devices had a number of disadvantages that frightened off most buyers. Forte's cyber helmet, introduced in the mid-90s, was bulky, ineffective and reminiscent of a medieval instrument of torture. The modest resolution of 640x480 pixels was clearly not enough for computer programs and games. And although later more advanced glasses were released, for example the Sony LDI-D 100 model, but even they were quite heavy and caused severe discomfort.Probably, for many of you such expressions as plasma technologies, plasma monitors sound with a certain degree of exoticism, and many, for certain, do not even imagine what it is. And this is understandable. After all, plasma monitors today are a rarity, one might even say a luxury, but, in any case, plasma technologies are very advanced and very promising technologies that are now at the stage of improvement. And, as you know, everything new and perfect always makes its way into life. And, perhaps, in the near future we will already see plasma monitors absolutely everywhere (at airports, train stations, in hotels and hotels, in various presentation rooms, and maybe even at your home), and they will no longer appear such a luxury that they have been until now.
Let's take a closer look at what plasma monitors are, or, in other words, PDP-monitors (PDP - plasma display panel), what they are for, what advantages and disadvantages they have in comparison with other types of monitors, and why still for many are exotic?
First of all, I would like to note that plasma monitors are, as a rule, monitors with a very large diagonal (40 - 60 inches), with a completely flat screen, and the monitors themselves are very thin (their thickness usually does not exceed 10 cm) and at the same time very light. And with all these advantages, plasma monitors allow maintaining the image quality at a very high level. And if you consider that there is a monitor of this size in front of your eyes, and which also shows very well, then I think that with such a monitor you will never get bored, for example, when watching films at presentations. This, in my opinion, is indeed a very effective and fashionable monitor.
Indeed, a plasma panel is one of the promising flat panel display technologies. This technology has been used for a long time, but the rather high power consumption and the simply gigantic dimensions of the displays have allowed them to be used only outdoors as huge billboards with video images. Today, many leading electronics manufacturers have quality plasma displays for professional and even home use in their product range. In terms of image quality and scale performance, modern plasma displays are unmatched. After all, they are able to provide, due to the peculiarities of the plasma effect, increased image clarity, brightness (up to 500 Cd / m2), contrast (up to 400: 1) and very high color saturation. All these qualities along with the absence of jitter are great advantages of such monitors. Plasma monitors, along with the above features, also have outstanding consumer qualities: the smallest thickness, which will undoubtedly help you save valuable room space (you can place your monitor anywhere: on the floor, on the wall and even on the ceiling); light weight, which simplifies the task of safely and conveniently placing and transporting the monitor; the largest viewing angle of the image (about 160 degrees). By the way, the viewing angle of the image is generally a very important parameter of the monitor. Imagine that you are looking at the monitor not at a right angle, but a little from the side, and suddenly the image begins to blur right in front of your eyes, and at a certain moment absolutely nothing can be made out on the screen. This disadvantage is inherent, for example, in many LCD monitors. Plasma monitors, due to the large limiting viewing angle, deprive you of the "pleasure" of observing the process of "dissolving" the image right in front of your eyes. To all of the above, it is probably also worth adding that plasma monitors do not create electromagnetic fields at all, which serves as a guarantee of their harmlessness to your eyesight and health in general. Think, for example, of radiation from cathode ray tube monitors. I think that none of you dreams of being left "without eyes" after several years of work behind a bad monitor. These monitors are also completely vibration-free. Unfortunately, the same cannot be said about CRT monitors with aperture grille. So, if necessary, you can place such a monitor in areas of frequent tremors or, for example, near a railway. By the way, a plasma monitor will look very good as a display at modern railway stations and at airports as an information video display.
It should also be noted that plasma monitors are resistant to electromagnetic fields, which allows them to be used in industrial conditions. After all, even the most powerful magnet placed next to such a monitor cannot in any way affect the image quality. Imagine how important this is in an industrial environment. As for the household level, you can safely place any acoustic speakers next to your monitor without fear of seeing various spots on the screen as a result of screen magnetization (let me remind you that the influence of electromagnetic fields is very strongly felt in CRT monitors). So, this moment gives even greater freedom to your actions on the design of your monitor and "hanging" it with all sorts of interesting "things" in the style of overhead speakers.
To the positive qualities of plasma monitors, you can also add their short regeneration time (the time between sending a signal to change the brightness of a pixel and its actual change). This allows such monitors to be used for video viewing, which in turn makes such monitors simply irreplaceable assistants in various video conferencing and presentations. And if to all the above list of advantages we also add the absence of image distortion and problems of convergence of electron beams and their focusing, which are inherent in all CRT-monitors, then, for sure, many of you will say: "Yes, these are just perfect monitors!" Yes, indeed, monitors are really good, and perhaps in the future they will become a worthy replacement for conventional traditional monitors. But don't jump to conclusions prematurely. Indeed, in any, even the most advanced technology, there are pitfalls that need to be polished. And, of course, plasma technology is not without its drawbacks, which, in fact, are now the main obstacles to promoting plasma monitors to the world market.
Let's take a look at the most basic disadvantages of plasma monitors. So, the main drawback that directly affects the low purchasing power of these monitors is their very high price. Indeed, the price of an average plasma monitor is now around $ 10,000. So a potential buyer of such a monitor today can be either some fairly large company for holding various presentations and video conferencing, or maybe just to raise their own image, or an individual for whom the price issue is considered secondary to ease of use. and the prestige of the device. Although, on the other hand, these monitors themselves form a new consumer niche, being almost ideal for showing commercials or transmitting public information. So the price factor now does not play a decisive role for many users when choosing such a monitor.
But, unfortunately, the disadvantages of plasma monitors do not end there. Also, a very significant drawback of a plasma monitor is a rather high power consumption, which increases with increasing the diagonal of the monitor. This disadvantage is directly related to the very technology of image acquisition using the plasma effect. This fact leads to an increase in operating costs for this monitor, but most importantly, the high power consumption makes it impossible to use such monitors, for example, in laptop computers. Those. such a monitor definitely requires power from the city network. So the impossibility of using batteries to power such monitors introduces some restrictions on the area of their use. But taking into account the general electrification, this disadvantage can be attributed to the category of insignificant.
Another disadvantage of plasma monitors is the rather low resolution due to the large pixel size. But, given the fact that these monitors are mainly used at presentations, conferences, as well as various information and advertising boards, it is clear that the bulk of the audience is at a considerable distance from the screens of these monitors. And this contributes to the fact that the grain, visible at a short distance, simply disappears at a great distance. These monitors really need to be looked at from a distance. And there is nothing to come close to a healthy monitor, because you have to cover the entire screen with your vision at once, so that you do not have to forcefully "jabber" your head in different directions in order to grasp fragments of the image in different parts of the screen. In connection with the above, rather low resolution, as a rule, is not a significant drawback of plasma monitors.
Another rather significant drawback of plasma monitors is their relatively short service life. The fact is that this is due to the rather rapid burnout of the phosphor elements, the properties of which quickly deteriorate, and the screen becomes less bright. For example, after several years of intensive use, the brightness of the screen may decrease by half. Therefore, the service life of plasma monitors is limited and amounts to 5-10 years with fairly intensive use, or about 10,000 hours. And precisely because of these limitations, such monitors are used so far only for conferences, presentations, information boards, i.e. where large screen sizes are required to display information. These monitors are especially popular at presentations, because in this case, the service life of the monitor is significantly increased, tk. it is relatively rarely in operation, unlike, for example, a plasma monitor, which plays the role of a round-the-clock video advertising billboard. Although, if you think carefully, 5-10 years of service with intensive use is not so little. For example, I can hardly imagine, for example, a home computer monitor that would work flawlessly for more than ten years. And if we also take into account the fact that now various manufacturers of plasma monitors are trying to do everything to increase the service life of monitors, then this shortcoming of plasma monitors will simply disappear in the near future.
Another disadvantage of plasma monitors is the fact that they usually start at forty inches in size. This suggests that making smaller displays is not economically viable, so we are unlikely to see plasma panels in, say, laptop computers. But this disadvantage of plasma monitors can be regarded as its advantage. Indeed, it was with the advent of these monitors that the barrier of the maximum possible diagonal of flat monitors was overcome. After all, ordinary LCD-monitors simply by their production technology cannot be made with a large diagonal. And the technology for the production of plasma monitors now makes it possible to produce monitors with a diagonal of up to 63 inches. Can you imagine what a giant? And I am sure that this is not the limit. But all this with its small thickness! But in the case of a monitor of such a huge diagonal, I advise you to be extremely careful, neat and careful when transporting it. And do not forget that he does not like strong vibrations, and mechanical damage, I think, will be completely useless for him. So, it is best to transport it in a special foam box designed for this very purpose.
Another, probably the last unpleasant effect possible with plasma monitors is interference. Essentially, interference is the interaction of light of different wavelengths emitted from adjacent screen elements. As a result of this phenomenon, the image quality deteriorates to a certain extent. Although, if we take into account the brightness, contrast and richness of colors, then the result of the appearance of interference on the monitor will be hardly noticeable. And the average non-professional user will probably just not notice any deviations in the image quality of your monitor.
Well, here, perhaps, are all the disadvantages inherent in plasma monitors. And if now we compare all the advantages and disadvantages of plasma monitors, then there is a significant predominance of all kinds of advantages. In addition, you probably noticed how we, as a result of reasoning, easily swept aside many of the shortcomings, and in some of them we saw positive aspects altogether. Moreover, one should not forget that technological progress does not stand still, and in the face of tough competition, plasma monitor manufacturers are striving to constantly improve the quality of their products. Thus, now more and more new technologies are constantly being developed that help to reduce the number of shortcomings and, at the same time, reduce the cost of plasma monitors. For example, Philips announced the price of its new Philips Brilliance 420P monitor below the mysterious $ 10,000 barrier. This fact already clearly shows that at the moment there is a clear tendency to reduce prices for plasma monitors, which naturally makes them available to a wider range of potential buyers and opens up new horizons for the use of plasma monitors.
In general, the plasma effect has been known to science for a long time: it was discovered back in 1966. Neon signs and fluorescent lights are just some of the uses for this electric current-induced glow of gases. But the production of plasma monitors for the mass consumer market is only starting now. This is due to the high cost of such monitors, and with their tangible "gluttony". And although the manufacturing technology of plasma displays is somewhat simpler than liquid crystal displays, the fact that it has not yet been put on stream contributes to maintaining high prices for this still exotic product.
How did scientists use plasma technology to create monitors? Plasma technology is used to create ultra-thin, flat screens. The front panel of such a screen consists of two flat glass plates located at a distance of about 100 micrometers from each other.
Between these plates is a layer of inert gas (usually a mixture of xenon and neon), which is affected by a strong electric field. On the front, transparent plate, the thinnest transparent conductors - electrodes are applied, and on the back - counter conductors. In modern AC color displays, the back wall has microscopic cells filled with phosphors of the three primary colors (red, blue, and green), three cells for each pixel. It is by mixing these three colors in certain proportions that different shades of a color image are obtained at each point of the monitor screen. The gas that is between the two plates goes into a plasma state and emits ultraviolet light. Thanks to the extraordinary color clarity and high contrast, a very high-quality image appears in front of you, which, believe me, will delight the eye of even the most meticulous viewer.
Let's now talk a little about the companies and markets operating in the production and supply of plasma monitors. Of course, now very many companies from different countries of the world have put their models of plasma monitors on the market, but various Japanese companies are the undoubted leader in the quantity and quality of the proposed models. Such, for example, as Hitachi, Sharp, NEC, Toshiba, JVC, Fujitsu, Mitsubishi, Sony, Pioneer, etc. In conditions of fierce competition, almost every manufacturer of plasma panels adds to the classic technology its own developments that improve color reproduction, image contrast, as well as expand range of functionality of the monitor. In the face of such a struggle for a leading place in the arena of plasma monitors, more and more new models of monitors from various companies constantly appear on the consumer market, which each time not only become better quality, but also constantly fall in price, which has a positive effect on the purchasing power of everything. more users. In general, in my opinion, the tougher the competition among the leaders in the production of plasma monitors will be (and, believe me, there is nowhere to be tougher today), the more high-quality and cheaper products we will receive.
The recognized leader in plasma technology is Fujitsu, which has the most experience in this area and has also invested a lot of money in the development of new monitor models. In 1995 Fujitsu entered the market with a new commercial Plasmavision series of plasma displays, which it continues to improve to this day.
NEC and Thomson have reaffirmed their commitment to collaborate on the development of flat-panel plasma display technology. The result of this collaboration is the introduction of a new Thomson model to the consumer market, featuring higher resolution thanks to high quality NEC panels. Both companies also intend to continue developing independently.
Pioneer offers professional plasma displays with arguably the broadest range of picture enhancement technologies available. The plasma display market is indebted to Pioneer for its ultra-clear picture technology.
Mitsubishi Corporation produces several lines of plasma monitors with a diagonal of 40 inches at once: the DiamondPanel series of TVs and the Leonardo series of presentation panels.
In general, each company "turns" as it wants and how it can, trying to bypass its competitors. And that's okay. After all, all this helps to improve the quality and reduce the price of plasma monitors.
According to Display Search, a flat-screen display market research company, the jump in sales in 2001 compared to 2000 was 176% (152,000 units in 2000, 420,000 units in 2001), although the studies cited primarily concern the US plasma market. displays. The figures for the European market and, even more so, for the Russian one look much more modest, but the dynamics of the industry's development is the same.
In any case, the prospects for the development of the plasma monitors market are evident. And now plasma technologies can rightfully be called technologies of the 21st century. Indeed, it is possible to trace the tendency of replacing traditional monitors with plasma ones. Although it is still very early to talk about complete displacement, it is still, for example, that video projectors for home theaters are being replaced by plasma monitors. In plasma monitors, unlike home theater video projectors, there is no need to place the projection device at a distance from the screen - with active information display technology, everything is housed in a flat case. It is also worth noting that the image on the plasma monitor screen is perfectly visible, regardless of the lighting conditions of the room, while in order to comfortably watch, for example, a movie in a home theater that works with a video projector, you just need to darken your room. Otherwise, on a bright, clear day, you will not be able to see a clear image. But on the screen of a plasma monitor, you will always see a rich image of excellent quality. So the video projectors, which have not yet reached the average user due to their very high price (a set of equipment for a home theater can cost 15-25 thousand dollars), will probably slowly, slowly, "sail away" into the background with the advent of more and more new models of plasma monitors.
Plasma monitors are a completely new generation of technology for displaying video and computer information, replacing the usual CRT monitors. Plasma technology is the technology of the future. Nowadays, the unique characteristics of plasma monitors open up wide opportunities for their use. With a minimum thickness of less than 10 centimeters, a wide viewing angle and low weight, plasma displays are gaining a solid reputation every day as a very attractive and seductive object that can decorate any wall. They can be used almost everywhere: at airports and train stations, in supermarkets and casinos, in banks and hotels, at exhibitions and conferences, at presentations and various shows, at TV studios and in business centers. And this list is not limited to the range of applications of plasma monitors. The unique characteristics of the monitors make them suitable for industrial applications as well. Convenient ergonomic design that allows you to place the monitor in any place convenient for you, and special branded, and therefore, by the way, not cheap accessories allow you to install monitors on the floor, hang them on walls with different tilt levels, hang them from the ceiling, etc.
In addition to plasma monitors, there is a whole range of additional equipment, such as speakers, all kinds of stands, bedside tables and mounting brackets, which are usually sold separately for a lot of money. They are expensive for the reason that, firstly, they are branded, and secondly, as a rule, they are made specifically for a particular monitor model, which means that they are ideally suited to this particular monitor in design. And with other additional equipment, the monitor, for sure, will no longer look so prestigious and neat. And in this situation, you will probably agree with me that it would be irrational to "mold" the wheels from the Zhiguli onto the Mercedes. And because of this, the user has no choice but to buy all these "bells and whistles" for his monitor at fabulous prices.
From all of the above, one conclusion can be drawn: plasma monitors have a great future, and we - ordinary users can only wait and hope that someday prices for these monitors will fall so much that they become affordable for us, and we can enjoy high image quality even at home.
Plasma screen
The plasma panel is a bit like an ordinary picture tube - it is also covered with a composition capable of glowing. At the same time, like LCDs, they use a grid of electrodes with a protective magnesium oxide coating to transmit a signal to each pixel-cell. The cells are filled with intert gases - a mixture of neon, xenon, argon. Electric current passing through the gas makes it glow.
Essentially, a plasma panel is an array of tiny fluorescent lamps controlled by the panel's built-in computer. Each pixel-cell is a kind of capacitor with electrodes. An electric discharge ionizes gases, converting them into plasma - that is, an electrically neutral, highly ionized substance, consisting of electrons, ions and neutral particles.
Under normal conditions, individual gas atoms contain an equal number of protons (particles with a positive charge in the nucleus of an atom) and electrons, and thus the gas is electrically neutral. But if you introduce a large number of free electrons into the gas, 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, negatively and positively charged particles tend to each other. In the midst of all this chaos, particles are constantly colliding.
Collisions "excite" the gas atoms in the plasma, causing them to release energy in the form of photons.
In plasma panels mostly inert gases are used - neon and xenon. When "excited", they emit light in the ultraviolet range that is invisible to the human eye. However, ultraviolet light can also be used to release photons in the visible spectrum.
After discharge, ultraviolet radiation causes the phosphor coating of the pixel cells to glow. The red, green or blue component of the coating. In fact, each pixel is divided into three subpixels containing red, green, or blue phosphorus. The luminous intensity of each sub-pixel is independently controlled to create a variety of color tones. In CRT TVs, this is done using a mask (and the projectors are different for each color), and in "plasma" - using 8-bit pulse code modulation. The total number of color combinations in this case reaches 16,777,216 shades.
The fact that plasma panels are themselves a light source provides excellent vertical and horizontal viewing angles and excellent color reproduction (unlike, for example, LCD screens, which require a backlight). However, conventional plasma displays normally suffer from low contrast. This is due to the need to constantly supply low voltage current to all cells. Without this, pixels will “turn on” and “turn off” like conventional fluorescent lamps, that is, for a very long time, unacceptably increasing the response time. Thus, the pixels must remain on, emitting low intensity light, which, of course, cannot but affect the contrast of the display.
In the late 90s. Last century Fujitsu managed to alleviate the severity of the problem by improving the contrast of its panels from 70: 1 to 400: 1.
By 2000, some manufacturers declared contrast ratios of up to 3000: 1 in panel specifications, now it is already 10000: 1+.
The manufacturing process for plasma displays is somewhat simpler than the manufacturing process for LCDs. In comparison with the release of TFT LCD-displays, which requires the use of photolithography and high-temperature technologies in sterile clean rooms, "plasma" can be produced in dirtier workshops, at low temperatures, using direct printing.
Nevertheless, the age of plasma panels is short-lived - quite recently, the average panel resource was 25,000 hours, now it has almost doubled, but this does not solve the problem. Plasma displays are more expensive than LCDs in terms of operating hours. For a large presentation screen, the difference is not very significant, however, if you equip numerous office computers with plasma monitors, the LCD gain becomes obvious for the buying company.
Another major disadvantage of plasma is its large pixel size. Most manufacturers are unable to create cells smaller than 0.3mm - this is more than the grain of a standard LCD matrix. The situation does not seem to be changing for the better in the near future. In the medium term, such plasma displays are suitable for home TVs and presentation screens up to 70+ inches in size. If "plasma" is not destroyed by LCD and new display technologies appearing every day, in some ten years it will be available to any buyer.
Probably, for many of our readers such expressions as plasma technologies, plasma monitors sound with a certain degree of exoticism, and some do not even imagine what it is. And this is not surprising, because plasma monitors today are a rarity, one might even say exotic, but, in any case, plasma technologies are very advanced and very promising technologies that are now rapidly developing. And, perhaps, in the not so distant future, plasma monitors will move from the category of expensive "toys" for the rich to the category of consumer goods. And even now there are certain prerequisites for this.
After all, the trend of increasing screen size is clearly observed both in the computer monitor industry and in consumer TVs. Monitors using CRT technologies have already approached the limit in their development, and their most advanced models, the screen size of which has reached 24 "(TVs have mastered slightly large picture tubes, nevertheless, more than 32" too large in weight and dimensions, especially in depth. And the cost of flat and light LCD displays with an increase in screen diagonal exceeding 20 "becomes too high. Therefore, oddly enough it sounds, plasma displays, which are about a few centimeters thick and light weight, can become a kind of lifesaver in order to create large screens. Due to this, despite the large size of the screen, they can be installed anywhere - on the wall, under the ceiling and even on a special stand on the table.The largest screen diagonal of the plasma displays produced today is 60 inches (over 1.5 meters) at a resolution 1365 x 768 pixels Most models have an aspect ratio of 16: 9, which is optimal for watching movies.In contrast to conventional TVs, the vast majority of plasma panels, even those intended for household purposes, do not have built-in TV signal sources. advantages of PDPs than disadvantages, because they have a large number of the most common A variety of inputs including analog video (RCA or SCART connectors), S-video, RGB (D-Sub and BNC), and digital DVI.
The history of plasma panels (or PDP - Plasma Display Panel), the technology of which is based on the effect of the glow of certain gases under the influence of an electric current, dates back more than 30 years ago, in 1966. Neon advertising signs and fluorescent lamps are the most striking examples of the practical implementation of this effect, which have successfully survived to this day. But the production of plasma monitors began only in the early 90s of the last century. The pioneer in the field of PDP was the Japanese company Fujitsu. The first commercial products of this company were used as information screens and displays at train stations, stock exchanges, and airports. Naturally, the first displays were monochrome and had poor image quality, but in just a decade PDPs not only caught up with the traditional CRT technology, but also surpassed it in many respects.
So what is a plasma display? It consists of two flat glass plates spaced about 100 microns apart. Between them is a layer of inert gas (usually a mixture of xenon and neon), which is affected by a strong electric field. On the front, transparent plate, the thinnest transparent conductors - electrodes are applied, and on the back - counter conductors. In modern color displays, the back wall has microscopic cells filled with phosphors of the three primary colors (red, blue and green), three cells for each pixel.
The principle of operation of a plasma panel is based on the glow of special phosphors when exposed to ultraviolet radiation, which occurs during an electric discharge in a highly rarefied gas environment. With such a discharge, a conductive "cord" is formed between the electrodes with a control voltage, consisting of ionized gas (plasma) molecules. That is why the panels operating on this principle are called plasma panels. The ionized gas acts on a special fluorescent coating, which in turn emits light visible to the human eye. Immediately I hasten to reassure those readers who are seriously concerned about environmental safety issues: the overwhelming part of the ultraviolet component of radiation harmful to the eyes is absorbed by the outer glass. The brightness and saturation of colors can be adjusted by simply changing the value of the control voltage: the higher it is, the more quanta of light gas emit, the more the fluorescent elements glow, the brighter we get the picture on the screen. Each cell is capable of glowing at one of 256 levels of brightness, which gives a total of 16.7 million shades of color for each individual triad (a set of three cells). To increase the contrast of the resulting image, black stripes are applied on the upper part of the inner partitions (edges) of the cells, separating the elements of the triad.
By supplying control signals to the vertical and horizontal conductors applied to the inner surfaces of the glasses of such a panel, the PDP control circuit performs, respectively, "line" and "vertical" scanning of the image raster.
Plasma displays are of two types - DC and AC. DC panels are a little simpler and, therefore, appeared earlier, however, most of the currently produced color PDPs are of the second type and differ from DC panels in that the electrodes in them are covered with a dielectric layer, which prevents the passage of DC current through the cell. Due to this, such panels have the property of "internal memory", that is, with a specially selected shape and amplitude of the voltage on the electrodes, the indicator cell can be either in the "on" state (the cell is on) or in the "off" state (the cell is extinguished) arbitrarily for a long time. To transfer a cell from one state to another, it is necessary to apply a single voltage pulse to it, therefore, the efficiency of converting electrical energy into light energy in AC panels is 5-10 times greater than that of DC panels. This provides increased image brightness and longer life of the electrodes, and, therefore, the AC display itself.
So what is good about them?
Firstly, the picture quality of plasma displays is considered to be the standard, although only very recently the "problem of red", which in the first models looked more like a carrot color, was finally solved. In addition, plasma monitors compare favorably with their competitors in their high brightness and image contrast: their brightness reaches 900 cd / m2 and the contrast ratio is up to 3000: 1, while in classic CRT monitors these parameters are 350 cd / m2 and 200: 1, respectively. (by the way, far from the worst of them). It should also be noted that the high definition of the PDP image is maintained over the entire working surface of the screen.
Secondly, plasma displays have a short response time (which many LCD models still cannot boast of), which allows you to use PDPs without problems not only as a means of displaying information, but also as televisions and even when connected to computer, play modern dynamic games. If we started comparing PDP and LCD technologies, it is important to note that plasma panels do not have another significant disadvantage of LCD monitors, such as a significant deterioration in the image quality on the screen at large viewing angles.
Thirdly, in plasma panels (as well as in liquid crystal ones), there are basically no problems of geometric image distortion and beam convergence, which are the real scourge of CRT monitors.
Fourth, having the largest screen area among all modern display devices for visual information, plasma panels are extremely compact, especially in thickness. The thickness of a typical panel with a screen size of one meter usually does not exceed 10-15 centimeters, and the weight is only 35-40 kilograms. Thanks to this, plasma panels can be easily placed in any interior and even hung on the wall in the most convenient place for this.
Fifth, plasma displays are extremely reliable. The declared service life of modern PDPs of 50 thousand hours (and in fact less than 9000 hours a year) suggests that during all this time the screen brightness will drop by half against the initial one.
Sixth, plasma screens are much safer than CRT TVs. They do not create magnetic and electric fields that have a harmful effect on a person and, moreover, do not create such a minor, but disgusting inconvenience, as the constant accumulation of dust on the surface of the screen due to its electrification.
Seventh, PDPs themselves are practically unaffected by external magnetic and electric fields, which allows them to be easily used as part of a "home theater" together with powerful high-quality speaker systems, not all of which have shielded loudspeaker heads.
Every day is not Sunday
With all the indisputable advantages of plasma panels, they also have their disadvantages, which restrain their widespread use. And the most, probably, the main one of these shortcomings is their too high cost, which sometimes "rolls over" for a 60-inch display for $ 20,000. So, a potential buyer of such panels today can be either some rather large company for holding various presentations and videoconferences, or maybe just to enhance their own image, or an individual for whom the issue of price is considered secondary in relation to ease of use and, most importantly, the prestige of the device.
In addition to economic problems, a number of technical limitations of plasma technologies have not yet been overcome. First of all, this is a low image resolution due to the large size of the image element. But, given the fact that the optimal distance from the monitor to the viewer should be about 5 of its "diagonals", it is clear that the graininess of the image observed at a short distance simply disappears at a great distance. Moreover, there are a number of special technologies to circumvent this limitation. One of them, ALIS (Alternate Lighting of Surfaces), developed by the Japanese company Fujitsu, provides an increase in vertical resolution without losing image brightness. For this, the number of pixels along the vertical has been increased, their size has been reduced, and the dividing gaps between cells have been eliminated. In order to eliminate the inevitable loss of brightness and contrast with this approach and achieve high picture definition, the company proposed to build an image first on even and then on odd lines of luminous pixels (the closest analogy is interlaced scanning of household CRT TVs). This method of alternation has significantly increased the brightness and increased the service life of the plasma panel.
Also, a rather significant drawback of a plasma monitor is the high power consumed by it, which rapidly increases with increasing the diagonal of the monitor. This disadvantage is directly related to the very technology of obtaining an image using the plasma effect: in order to light one pixel on the screen, a meager amount of electricity is required, but the matrix consists of millions of cells, each of which has to glow all the time the monitor is operating. This fact leads not only to an increase in operating costs for this monitor, but high power consumption seriously limits the range of PDP applications, for example, makes it impossible to use such monitors, for example, in laptop computers. But even if the problem with the power supply is solved, it is still not economically profitable to manufacture plasma matrices with a diagonal of less than thirty inches.
Well, here, perhaps, are all the disadvantages inherent in plasma monitors. And if we now compare all their advantages and disadvantages listed above, then there is a significant predominance of the former over the latter. Yes, we must not forget that technological progress does not stand still, and in conditions of fierce competition, plasma monitor manufacturers are striving to constantly improve the quality of their products, which, along with a slow but steady decrease in their cost, makes PDP available to everyone. a wider range of potential buyers. We can only hope that sooner or later we may well be among them, dear reader.
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