The Display Devices in the Television Production
By Leonid Chirikov, Lev Ivin

Functions of the display devices are always different and their role is significant. Today the convergence of the television and computer techniques can be considered as committed one. At least the contemporary computers are capable of extracting and reproduction with the necessary quality the video and the TV sets through the appropriate interfaces can reproduce the electric graphics. At that the defined leveling of the facilities of the professional and domestic destination can be noticed in what is regarded as their main function. So about the PC class of the IBM row can be said with some sureness that this is professional or, on the contrary, domestic desktop computer only in cases when the software is known. The same is regarded to the display devices. Often the differences can be only mentioned not by the claims to the main function, which is the quality of reflection, but by the set of the additional and service functions of the TV in general. More than that the levering starts already from the production. Today many companies are manufacturing the production of professional and domestic destination at the same time, what seemed to be a venture earlier.

All these are the trends, which should be considered and taken into account at the appraisal of the contemporary condition of the display devices. And more, during examining some facilities, for example, with the purpose to buy it, it is useful to remember that the developing and manufacturing companies sometimes stick to the tactics of failure to mention some specialties and parameters which might decrease the interest to their production from the position of this or that application.

Practically everyone knows, understands and is relatively tied from the television tube. And its best and worst sides are well known. A lot is known about the advantages of the liquid crystal and plasmic boards. And all of us know them at the very least. But only the narrow caste of the specialists know, but only suspects, that in the up-to-date and unbelievably perspective (not only in the prospects of the interested companies, but in fact) there are some hidden problems.

During the seventy-year old history of the electric television there was scored for sound a big number of projects of creating the display devices based on the very different physical effect and sometimes most unbelievable ones. Today, for example, one idea of the epoch of the mechanic television is provided on the market, but at this time with the serious chances for the success. It is the idea of the original (due to the antiquity of the 'initial material') project of the reflection based on the huge amount of the controlling micro mirrors. Let's point out that the forgotten prototype had much more modest materials and much smaller success about a hundred years ago. The contemporary technologies are capable for the much more, to face the truth.

The cathode-ray tubes (CRT) can not be separated from the television and they were and probably will become its symbol. The television is already dropped under the pressure of the charge transfer device by the transfer tubes that are yet receiving in the busyness. V.K. Zvorikin who was the founder of the electric television gave the name 'kinescope' to the reflecting (receiving) CRT in the 1928. Till today they are called like that all over the world.

Only in the second half of the last century there appeared the first messages about the unbelievable at that time and now very serious and stubborn competitors of the kinescopes which have contrasted with their holiness and relatively large volume the old dream of the board performance. At first the facilities based on the liquid crystal display (LCD) and then the plasma display panel (PDP) had appeared. Now the matrix panels based on the light-emitting diodes (LED) are about to appear. In the general variant these panels are assembled from the separate devices.

Diagonal size diagram of LCD, CRT and Plasmas. Red - maximum, blue - minimum

The diagram shows what intervals of the possible sizes of the screen diagonal the LCD, CRT and PDP cover correspondingly. It is seen that the displays based on the liquid crystals are the 'minimalists'. The upper limit of the LCD diagonal size is now about 80 cm. (30...32") and the lower is about 5 cm. but this is not the minimization limit. There are no principle prohibitions, but the technical restrictions are significant. The LCD is the light, modest in claims for the electric power. The technical size restrictions are the primitive homogeneity of the parameters on the large (at the height) and are micro small squares o the screen. The kinescopes reached the metric note (40") and that seems to be forever.

The plasma display panels are the natural giants, the diagonals of 1.5 m (60") are their worthy level. To say the truth, the further growth of the diagonal is not limited theoretically, but is restrained by the rapidly growing power consumption and the progressive mass growth. And that is in principle. The plasma is the power-consuming process and the growth of its volume provokes the quadratically growing current. It is interesting that at least for the plasma panels of 50...60" the numerical characteristics of mass in the kilograms and of the diagonal in inches almost coincide or if they differ then by a negligible margin. The example (see the general table of the PDP) the mass of the Revolution 10 model of the Dream Vision Company with the diagonal of 61" accounts for 61 kg, and GD-V500PZU of the JVC Company with the 50" diagonal is 45 kg. The expansion of the plasma panels is now on the decline. The note 80 cm. is reached already.

The obstacle for the further miniaturization of the plasma displays is the technological difficulties. In the cells of the panels, which are the millimeter minors at the smaller sizes the instability of the plasma becomes a difficult issue. The decline in the sizes makes the difficult task of the phosphors security from the relatively aggressive plasma more complicated. At that the bombing of the phosphors by the quick electrons of the plasma is a little disaster. The ultraviolet and the massive prodigal ions are more serious. The consequence is the gradual changing of the color temperature. Now the less important, but not excepted is the burning-out of the phosphors with the full failure. All that and lots more create the problems that can be solved but are still very difficult. The LCD, which has the advantage in the mass of the devices and power consumption, can become an obstacle for the miniaturization. To be honest we can mention that the PDP's advantages are the high brightness and contrast range.

The display devices for the professional television on the contrary to the domestic TV set don't need the high-frequency part, which provides the broadcast receiving, at all. There is no necessity in the service functions such as 'picture in the picture' and other contrivances. But the general set of entrances of the full and component signals of the analogous television of the various systems of the digital coding, chrominance and RGB signals, series and parallel digital signal, SDI, etc are the integral requirement to the information display devices of the professional assignment. This is the principal boundary line of the domestic and professional display devices. There is also another boundary line. In the domestic and professional reproduction the criteria of the quality appraisal are not quite equal.

The Kinescopes

It is unlikely that the modern person, who has been setting in front of the TV or computer since early childhood need an explanation of what is kinescope. We'll remind just the main physical principles of the operating and construction of that device. For the uninitiated the kinescope is the big and heavy retort. All the electronic processes in the kinescope occur in the deep vacuum. The retort is the reliable secure of the vacuum, which resist the atmosphere pressure. The big sizes quadratically lead to the swelling of the retort and to the mass increase. The narrow part of the kinescope retort is cathodic, here three are electric cannons which form the RGB electric beams are situated. The focusing and the scanning system are magnetic. All that is the electron optical part of the facility. In the anodic part the mask which controls the color reproduction is situated. Behind the mask on the large surface of the screen part of the retort there are the special electroluminescnet substance is applied in the view of spots, which at the bombing of the relatively quick electrons radiate the color in the red, green and blue part of the specter. On the television screens it is general the delta-like disposition of the round spots of the RGB phosphors or the shape of the phosphor spots is rectangular, the sizes and correlation of the sides correspond to the standards on the displays.

The not less rich set of the aberrations is inherent to the electron optics than to the general optics. The specialists had to work hard to clean the television raster from the aberrations to the acceptable level. By many parameters that are important, in particular, for the row of applications in the professional television the display devices on the kinescopes surpass their panel competitors. This is especially important when we are talking about the display devices used as the video monitors, i.e. the facilities, which provide the comparative analysis in the conditions of the visual control. Those are exactly the video monitors in the directors and technical control rooms, for example.

For the video monitor used parallel with the visual control the smoothness of the brightness characteristic is important, which should be linear on the relatively extensive interval. Very close to the brightness characteristic is the continuous-tone one. This list can be continued by the list of the parameters of the display devices, which should be maintain on the maximum high level if it is used as the professional video monitor.

The director and studio engineer has not only to look through the picture on the screen of their video monitors appraising the general quality, but also through the window to the studio compare with the real which they see in the studio. Such a comparative analysis of the situation allows, for example, noticing the slight differences in the color rendition, finding the reason and eliminating it. But that is possible only in cases when the specialist trusts the video monitor in the fidelity of reproduction. The tracking after the actions in the studio even at the working on the monitor on location doesn't give and can't give the full information during the process of preparing and then conducting of the shooting

It should be pointed out that the display devices, even superior in the main function, which is the reproduction quality, far not always could be recommended as the video monitors. The saturated color, good dynamic diapason, perfect contrast, high clearness and other are for sure important in the viewing room where between the real action and its reproduction is a very long distance. Certainly, this is also good for the video monitor. But the neat correspondence of the reproducing and initial, for example the parameters named earlier, is necessary and important.

Say, the Moscow river on the screen of the TV sets we almost always see blue, and do we actually see in live? The television leaves always are reproduced green but not dusty as they usually are. Such things happen not without the disturbance of the video director. The decorating of the reality as the artistic method is acceptable and usually necessary, but that is exactly what is forbidden to the video monitor at the first place. That is why the video monitor faces the very strict requirements and especially by the parameter of the neat correspondence to the realities, otherwise you won't be able to determine who is lying. On the shooting area all is possible: the light had 'strike out', the color set of the cameras had stripped, and much more other. Looking only on the monitor or only on the area it is usually impossible to notice the defects. The correspondence is the parameter, which never cited in the prospects on the display devices. But that parameter even not declared includes in the company's guarantees, which specialize in the production of that exact facility for the professional television.

The far not simple devices on the kinescopes are the best way adapted for the operating in the conditions of the visual control now. The correspondence parameters are supported in them by the complicated systems of the internal control and diagnostics, which cannot be find in other display devices. The video monitors are perfectly made by the Barco Company. The companies Sony, Panasonic, JVC Professional, Hitachi should be added here. Other words, the sense of the video monitors is understood only by the companies, which operate in the developing and production of the professional techniques for a long time. The video monitors are always expensive facilities. And that is far not accidental.

The appraisals of the international experts forecasting that by the year 2010 the kinescopes would be pushed out from the domestic reproduction, their professional use should not be prolonged, where the alternative display devices are not convincing in everything yet.

The Liquid Crystals

The liquid crystals are the remarkable object of nature. The interest to them appeared only in the XX century, in the first half laboratory and in the second half practically. The first operating steps of the LCD was the medicine where the exceptionally high sensitiveness of the liquid crystals to the temperature anomalies made them an effective instrument of the visualization of the temperature fields. The contemporary infrared imagers had actually pushed out the LCD from the thermal imaging. However the specialists had paid attention to the sensitiveness of the liquid crystals to the electric field and soon they became the working elements of absolutely different indicator facilities. Now the LCD dominate in the general field of application: from the indicators of the electronic wristwatch to the facilities of the special assignment and usually top secret. More than a quarter of a century ago the were undertaken the first successful attempts of the realization based on the LCD flat, light and thin screens for the images reproduction. That is the prehistory.

The crystals are the substances the condition of which can be determined by the long range ordering. Other words, the long range ordering is the variant of the 'registration' all of the molecules have to be on their places. Let's point out that such an order is the fundamental and the most well-spread in the nature of the solid nature. Any molecule of the liquid opposite to the solid is free in its travels besides for the intersection of the borders. That is what the theory of the aggregate condition of substances proclaims. It excludes the long range ordering in the liquids and so the liquid crystals. But the theory itself is stated for the large number of substances. In the straitened circumstances and behavior of the substances and the people's behavior it can change significantly, as it is well known. In case of the liquid crystals the straitened circumstances can be the pellicle, relatively thin, so that the molecules would 'feel' not only the neighbors but also the limits. The liquid crystal condition is possible only in the substances which molecules are sharply anisotropic in shape. These are, for example, the filiform or the dumbbell shaped molecules. The molecules that resemble the discs willingly gather in 'columns'. One more interesting shape of the molecules is the comb-shaped, which belongs to the substances that are capable of forming the liquid crystals.

To put the matches into the matchbox tightly the 'long range ordering' is necessary. The same corresponds to the aeolotropic molecules. The interaction powers make them to orient by one another by the determined way. By the close look at the behavior of the liquids with the aeolotropic shaped molecules the scientists noticed that even in the big volumes the molecules of the liquid crystals gather in small groups with the priority orientation or domains. And the warmth movement forces to break this constantly renovating self-orientation again and again.

In the thin pellicles the limits, which are not only capable of stabilizing of the domain form but the domains themselves are oriented in space by the determined order, interfere in these processes significantly. As a result there appears that what can be called the long range ordering and the condition of the substance can be called crystal. The liquid crystals are basically the unstable substances, which is situated between the order and thermal destruction. That is why they are especially sensitive to the external effect, which disturb in their fragile balance. This sensibility is the great advantage and at the same time the significant disadvantage from the position of application of the liquid crystals. Actually, all the internal effects on the LCD except for the main are capable of presenting as the drawbacks.

Also the cyclic violations or the changes of the character of the order are connected with the molecule travel and that is the inertial mechanic processes. That is why the time of the relaxation of the liquid crystals is high (few milliseconds) what can become a disadvantage for some applications. That is exactly what lowers the value of the LCD for some applications in the TV production.

For example the Sharp Company had successfully developed the chamber video selector based on the liquid crystals and applied it in its video cameras. In the '625' magazine the materials about the video projectors D-ILA of the JVC Company, where the LCD modules operate as the light-valve grids, were published for a few times. The projectors got the highest appraisal. The example of such kind can be multiplied. But you needn't hurry, for example, with the recommendation of the LCD to the post of the video monitor. The sensitivity of the LCD to the external conditions here is the unfavorable factor. However the small mass and the lower power consumption are capable of becoming the main argument at the choice of the monitor, say, for the video journalist complex or for the similar mobile set for the out works.

There are the three types of the liquid crystals. These are the smectic, nematic and cholesteric. The most 'crystal' of them are the smectic ones. The molecules of the smectic type gravitate towards the two-dimensional order. They understand the 'align' command and independently lines up in the rows on the, so-called, smectic planes and into the ranks by the nematic. Other words these are the well-trained battalion of the molecules on the LCD parade ground. The order of the nematic sphere is lower than at the smectic. The nematic molecules are 'licensed' to shift by their 'long' axis. Such an order is somewhat one-sided and the reaction to the external effect is much faster than in the smectic case. This is important for the 'candidate for work' in the display devices.

Above the liquid crystals of the cholesteric type were mentioned. Their most famous representative is the dolefully known cholesterol. The specialty of the molecules of the cholesterol is that at the relatively high side tension the tops of the molecules are pushed aside. That is why for them the energetic profitable is such a position when the long axis of the molecules are a little unfolded. That is why to the nematic mainly flat orders of the molecules the spiral structure (the so-called twist-effect) is added. Let's notice that the substances claiming to be the liquid crystals in general are scarce. Never the less the search of the substances of the quality is continuing. At the last time the specialists look to the organic polymers more attentively. At that they take into consideration the special synthesis of such polymers to the LCD tasks.

Strictly speaking, for the liquid squeezed between two plates the direction orthogonal to the plate is the only orienting factor. That is why molecules line up into the long axis mainly along that direction or along the surface of the border, everything depends from the fact what is attracts and what repels the plate surface. In that case in the direction parallel to the plates the molecule is still free. At that is not enough for the stability of the reproduction where the more strict orientation of the molecules is necessary. They should be fixed somehow also on the surfaces parallel to the plates. For that purpose on the plates the strokes (superficial riffles) are drifted. If the direction of the riffles on one and another side of the plate coincides then there appears the preferential orientation of the molecules and along the normal of the plate and along the strokes. The preferential but not full the orientation becomes only due to the warmth travel, which is the enemy to the full order. The best candidates for that orientation variant are the smectic substances, the nematics are also appropriate. If the directions of the strokes on the plate are mutually orthogonal then there appears the twist structure. It is contra-indicated to the smectics, but is natural for the cholesterol. The nematics can be also appropriate in that case. In the optic relation the liquids with the linear structure of the orientation are similar to the double refraction spheres (the two rays are spread with the different phase speeds and orthogonal directions of the linear polarization). The spheres with the twist structures are similar to the optic active assets (two rays with the circular polarization clockwise and anticlockwise.

The LCD cells are the two transparent dielectric (for example, glassy) parallel-sided plates with the marked transparent conductors. On each of the plates they form the system of the parallel electrodes but in the relation to one another they are crossed (see the picture). The crossed electrodes form the honeycombed structure. Each cell (honeycomb) is the screen element, three cells with red, green and blue filters correspondingly are the pixels. The electrodes of one plate give the impulses corresponding to the counting out of the RGB constituents of the image horizontally in series and the electrodes of another vertically. On the each tact one cell drops by the impulse. On one of the plates (outlet) the RGB filter is marked, through another all the cells are equally illuminated.

Basic construction of LCD

For the control of the screens the small electric potentials that are capable of significantly changing the physical parameters of the liquid stuff are needed. Actually everything changes rather significantly. These are the warmth receptivity, the ratio of the light refraction and much other. The electric impulse, in particular, may lead to the chaotic reorientation of molecules and, at the end, to the local anomaly of the ratio of refraction, absorption and dispersion of light. As a result the area under the electrodes on which the according potential is given becomes the center of the diffusive light diffusion. Exactly this effect is used in the facilities of indication and reflection based on the liquid crystals. In the LCD the more thin effects of the phase light modulation, which is provoked by the controlled (with the help of the electric potentials) changes of the light diffusion ratios in the liquid crystal sphere are used. The dependence between the diffusion ratios or, what is the same, phase speeds of light are called the electrooptic effect. Exactly for the linear electrooptic effect become possible in the LCD cells the riffles that were mentioned earlier are necessary. In the LCD cells the so-called longitudinal electrooptic effect is used (the electric field and direction of the light expansion coincide).

In the aeolotropic sphere the light wave is divided into two components with the orthogonal polarization directions and the general wave vector. The own polarization directions in the birefringent medium are linear, in the optic active they are left are right circular. The phase speeds of such components in general are different and inversely to their diffusion ratios, the difference of which depends on the tension on the cell. At the end between the components at the passing of light through the cell accumulates the phase difference, which is proportional to the tension. It is necessary to transform these phase difference in the appropriate brightness changes. With that purpose the cells should be situated between the crossed linear or circular polarizers. On the exit due to the interference the phase changes will be transformed (quadratically into the changes of the activity or brightness, what is almost the same. The optic scheme of the LCD cells application as the electrooptic grid is explained by the picture.

The electrooptic grid has the flat dynamic (brightness) characteristics. Actually that is the sinusoid:

Y/Y₀ = 0.5·cos(U/U₀)

Where Y is the current brightness of the cell; Y₀ is the maximum brightness; U is the current tension on the cell; U₀ is the tension of the maximum brightness, it depends from the sphere parameters and the length of the light way in the cell. The represented formula relates to the ideal case of the parallel light flow through the cell. The real flow always has some angle of divergence. The formula becomes much harder, but the sinusoid character of the curve stays. The most unpleasant is that the appearance of the constant component of the light on the exit is connected with the divergence. It is proportional to the divergence angle. That is why the LCD are problem in such a characteristics as the contrast range of the reproduced image. The effect of 'dripping' of the divergent light is the principal disadvantage. But, actually, it can be weakened with the help of some devices. Never the less in the rush for the high contrast of the LCD it is the weakest runner.

Modulation characteristic (red - ideal, blue - with account of divergence)

On the picture the dynamic characteristics are represented: ideal and with consideration of the light divergence. For the realization of the electrooptic conditions of operation of all the display the polarizing pellicles of linear or circular polarization are stuck on its entering and exiting surfaces.

In the last years into the represented easy construction of the LCD display the significant corrections are carried in. Very perspective direction is the active control of the LCD cells with the help of the thin-film transistors, the so-called TFT technology. For that purpose on the plate the thin layer of the crystal or amorphous silicon is applied, on which the technology forms the transistors. Of course, that complicates the production of the LCD displays, but also provides the big profits as it allows increasing the quality of the reproduced image significantly by many parameters, for example, contrast, to weaken the effect of slow relaxation, opens the perspectives of increasing of the screen size up to 80 cm, and even more in the future.

In 2000 the Toshiba Corp. and Matsushita Electric Industrial Co (trade mark Panasonic) united into the consortium, whose main target was the creation of the new generation of the LCD, including based on the TFT technologies. In this direction also Sharp is working especially actively. It is necessary to say that this company already in 1973 was the first in the world that started to work with the LCD as with the perspective direction in the field of the display devices and had achieved significant successes. Sharp was the first one who offered the use of the thin-film transistors for the increase of the reflection quality, reproduced by the LCD displays, and is now developing the new direction connected with the digital processing of images. The serial production of the last models, which are the display devices based on the liquid crystals is worked out. At present the situation on the market is next: the LCD are heavily pressing the kinescopes on the market of the computer displays, they had also seriously declared themselves on the television market. Many experts, especially in the USA and Japan suppose that that by the year 2010 in all the developed countries the LCD will almost absolutely replace the kinescopes with which they are actually dividing the niche of the display devices with the screens of the diameter less or about a meter.

The Plasma Display Panels

In the PDP such a physical effect as the gas discharge is used. The gases become electroconductive as the result of the ionization. There are distinguished the dependent (ionization due to the external effect) and independent (ionization due to the own current) discharges. The typical device where the independent discharge is used are the discharge lamps, for example, daylight lamps.

Typical volt-ampere characteristic of independent gas discharge

The independent gas discharge appears when between the two objects, later electrodes, creates a big electrical potential. When it achieves some critical quantity Udr, there appears the disruption and the gas discharge lights. In that phase (sector ab on the picture) it is called the normal punky discharge. The character peculiarity is the falling volt-ampere characteristic. It is important to mention that the potential, which maintains the normal punky discharge, is smaller than the lighting one. The normal punky discharge is used in the PDP sometimes with the entering into the spheres of the anomalous discharge (the cd area).

At the gas disruption (lighting) the streamer channels or the area, which contents the ionized gas or plasma, is formed. The discharges are always accomplished with the light emanation that can be also seen ultraviolet, which is often the main component of the emanation. The mechanism of the emanation is following: the recombination of the plasma ions till the neutral molecules at the pushing with the electrons. The transmitting processes connected with the disruption and formation of plasma occur rather rapidly (10-7 sec and less). After that the punky discharge becomes equilibrium, i.e. the processes of the recombination and ionization are balanced in it. In the phase of the anomalous discharge the compression of its positive column begins. At that the column teats from the walls of the vessel that limits the discharge. in the d point the discharge becomes arched.

The ultraviolet emanation of the plasma transforms into the visible one with the help of the phosphor. In principal, the over emanation with the decrease of the photon energy is widely spread in the nature. The plasma panel is divided into the cells of the rectangular shape. The general amount of the cells is over a million. In particular, the panel of the 16:9 format usually has 853 pixels across, by three RGB cells in each. The total is about 2559 cells. Accordingly, vertically it should have about 480 pixels. In general such a panel consists of 1228320 cells. The concrete sizes of the cell depend on the diagonal magnitude. For example, at the diagonal of 42" (107 cm) the step of pixels accounts for 1.1 mm. So at each cell with taking the thickness of the partition into consideration there is just about 0.37 mm.

As we can see, each cell of the PDP is the miniature gas device. The honeycomb cell structure is situated between the two plates. One is the back wall of the panel and another is exiting and that is why it should be transparent in the visual part of the specter. Between the plates the rather strict construction is situated, which actually forms the side walls of the cells. We'll also mention that in its construction of the PDP the Pioneer Company applied the 'waffle' structure (The Waffle or Deep Waffle technology). Each cell is the cavity in the substrate, which has the rectangular shape. The advantage is the full isolation of cavities. The pictures explain the typical construction of the cell and base construction of the panel.

The cell of the plasma display panel

The base construction

The dielectric layers separate the electrodes from the chamber. The lower (on the picture) electrode connects to the back dead wall that is why it is metallic. The electrodes from the side of the exiting plate are made from the transparent current installing material. In principal, the protection layer, the glass exiting plate and other 'transparent' elements of the construction do not let the ultraviolet to pass through and that is why prevent the penetration of the ultraviolet emanation into the 'outer world'.

The phosphor covers the back and partly side walls of the cell chamber. Naturally, the phosphors of three different mixtures are used, that accordingly emanate the main colors: red, green, and blue. The cells are stuffed with the inert gas, this is neon or xenon, rarely helium. The mixture of these gases is also used. The gases are situated in the rarefied condition. The underpressure is what decreases the potentials of the lighting and equilibrium discharge. The viewed construction of the cells became formed far not at once. The plasma is capable of fast destroying the phosphor covering especially on the state of the normal punky discharge. That is why the search of the optimal configuration of the cells was conducted by the cut-and-try method, till the problem of the effective separation of the plasma area from the phosphor was solved. And still the 'burning-out' and, as a result, the changes of the color temperatures, in particular, were and still remain to be a problem.

One more basic problem connected with the PDP is the high power consumption. The plasma is the machine of electric current transfer into the ultraviolet with the low efficiency. Each cell of the plasma panel of 1/3 mm size consumes about 1.5 microampere. This is the decent current for such a 'miniature'. The standard one million (or more) cells consume over 1.5 A of current/ At the potential of the equilibrium discharge of 20 V this comes to 300 Wt of the consumed power (the estimate is done for the 40" panels), nearly same or a bit more (350 Wt) is consumed by the PDP with the 42" screen cornerwise. The 1.5 times increase of the screen diagonal from 40" to 60" leads to the according increase of the cell sizes and quadratically, i.e. in 1.5 * 1.5 = 2.25 times increase of the power consumption. So the general power consumption should increase from 300 to 675 Wt what we can nearly see (see the general table).

The comparison of the PDP with the kinescope reflection shows that at the equal 32" screens the PDP power consumption is 3 times higher. At that is also the problem of the warmth pipe-bend what is at smaller panel volumes becomes a very difficult issue. However, the problems are known and they are fought somehow. One of the approaches is the equipment of the plasma device with the shot store, which controls the distribution of the source power among all the pixels proportionally to the corresponding brightness. The Nec Company calls such a processor PLE (Peak Luminance Enhancement).

The Brightness and Contrast of the PDP Image

The peculiarity of the PDP is the high dependence of the brightness of the screen image from the content of the reflected information. Sometimes in the ratings for the PDP the two values of brightness are mentioned. On of them (brightness panel, white peak or w/o filter) means the maximum of brightness by the ratings of the plasma panel producer, and the smaller in value second (brightness of set) is the realized brightness value in the concrete production with the plasma panel, used as a spare facility. That value is much smaller than the white peak as it is mentioned with the taking into account of the light losses on the filter, protecting the screen glass with the anti-refined covering and restrictions of the power supply. This restriction is usually brought in with the purpose to simplify the warmth conditions of the plasma panel and the decrease of noises from the operation of the build-in ventilation system. The problem of the warmth deflection appears due to the fact, that the gear the PDP profitably varies from the kinescope TV sets by the better clearness of the image and the construction compactness, but significantly yield to them in the economy. For example, we get that in the much smaller internal volume of the gear from the 32" PDP the order more warmth than the TV with the same screen diagonal. That is why the PDP are equipped with the processor, which distributes the according part of the power supply source by all the pixels of the plasma panel proportionally to the required from them brightness according to the signals of the shot memory. The producers do not usually said about the methods of the measuring. It is only known that the brightness and contrast parameters of the PDP usually change on the image that includes 16 equally divided small white areas with the maximum brightness on the black background. At that the brightness defines as the average value by the 16 areas and the contrast as the ratio of the average brightness of the white areas to the brightness of the black background. So the rumors about the high contrast and brightness of the 'plasma' image (and that is exactly from the rumor category, as the companies don't declare about the methods of measuring) are much exaggerated. For example, at the testing of the good plasma panel with the rating brightness value of 400 cd/m2 and the contrast of 3000:1, conducted by V.P. Samohin and I.B. Sokolovain the laboratory of the Stereo & Video magazine with the use of the certified by the All-Russian Research Institute of Television and Radio Broadcasting luminance meter L1009 these criteria happened to be absolutely different. So the brightness of white field was only 48 cd/kV2 and about 100 cd/kV2 at the changes along the chess field, i.e. smaller than at any contemporary TV set. The brightness of 185 cd/kV2 with the contrast of 600:1 was found at the show on the 42WP16 black-and-white field that includes 16 uniform distributed white areas on the black background. It is interesting that at the changes by the same field the 29" TV set Panasonic TX-29GF95T showed the parameters 300 cd/kV2 and 250:1. So you should be careful with the receiving of the declarations of the superior parameters for the plasma monitors.

Yes, the display devices based on the processes existent in the plasma are complicated and capricious. But the most important is that they remain the great reserves for the increase of the parameters due to the different technique-technological devices and it is useful to take a better look at some of them.

Cell status cycle in the data recording mode

Not so long ago (10.09.02) the Nec Company conducted a seminar in Moscow, where, among the other told about an interesting method of the cell control, which allows highlighting the cells not one after another, as it is traditionally done, but in the big blocks. With that purpose on the cell picture the data electrode is foreseen. The full cycle of control is eight stations of the condition switches. These stages are explained by the block of pictures, which numbers correspond to the station number.

1. The reset state. All the electrodes are situated under the conditional zero potential.
2. The starting discharge. The punky discharge is lightening, the current in the plasma is establishing, which corresponds to the lower potential of the normal discharge. The potential of the Sustain wire (the supporting electrode) is positive. The emanation from the cell is almost absent. On the stage the primary ionization of gas, which provides the turning on of the discharge without lightening (dependent discharge) on the next stage, is created.
3. The discharge of the data recording. The Sustain wire turns off. On the Scan (of control) and Data (of address) wires the short signal are sent with the swing accordingly -180 and +70 V. The discharge is formed in the area between the Scan and Data wires. The commutation of the cells is performed in the general condition along the lines and progressively vertically. The time of the line commutation is 3 microseconds or 1 nanosecond per line if 1 thousand pixels.
4. The storage of data. All wires are turned off. An the Scan and Data wires the electric discharges are preserved in the cells where the tensions on the 3rd stage had entered at the same time. These discharges create the field, which supports the ionization with the 250 V potential.
5. The first part of the main discharge. On the Scan wire the potential +40 V is given, on the Sustain wire -180 V. By that the equilibrium puncky discharge with the general potential of 250 + 220 = 470 V, which is enough for the plasma emanation of the intensive ultraviolet emanation, is provoked.
6. The second part of the main discharge. The condition of the support of the plasma discharge is performed. For that in each 2.5 microseconds the polarity of the Scan and Sustain potentials is switched. The swing of the switching impulses is 22o V.
7. The extinguishing of the discharge. On the Scan and Sustain wires the potentials are lowered to the level used on the stage 2. The ultraviolet emanation disappears.
8. The cell in the reset state. The Scan and Sustain wires are closed-looped, the ionization of the gas sphere stops.

The viewed earlier cycles of the PDP cells reduction into the light emitting condition is rather bulky and needs explanations what is it done for. And that is planed for the recording of the data into the cells at first and only then to light them out at the same time. And that is the way to the significant increase in the image quality, which approaches the film in a sense. But, say, that according to the television field this is not quite successful. The estimates show that at the bringing earlier parameters for the support of the emanating condition in the 15.26 ms (the active part of the TV field) fall only 6100 impulses of the polarity on the 6 stage. In that case the cells can be situated in the turned on or turned off condition. That means that the scale of gray doesn't transmits and only six color tints are reproduced. The exit is in the 'splitting' of an idea. The procedure of the recording and reflection can be divided, for example, into eight sub-fields. And that, in particular, means the thrice-repeated decrease of the brightness.

From the very beginning of the increase by the plasma panels it was mentioned that the color characteristics of their emanation are far not the ones that are needed for the display devices of the color images. For the correction the separating filters RGB are usually used. The Nec specialists thought to cover the cells with the RGB CCF (Capsulated Color Filters) filters. Such a filtering, which at a first glance can seem a fantasy on the 'butter is buttered' theme actually is useful by that it allows removing from the phosphor emanation all excess and also to cut off the emanation of the plasma in the visual sector of the specter. As a result the light flow of the external light-striking diminishes only in 1.6 times, but in three times as it could have been if that technology CCF was combined with the filter of the color selectivity AccuCrimson for the correction of the red parallax of the color palette.

The Matsushita Company approached the increase of the PDP parameters of the Panasonic mark very ingenuity. Plasma AI (Adaptive-Brightness Intesifier) is the technology in which the double scanning at the recording with the adaptive discretization on 10...12 sub-fields are used. It depends on the types of the image fields (movie of photograph) and from the average level of the signal on the sub-field. The amount of the Sustain impulses in the darkest regions in traced by the Real Black function. Among the original offers of Matsushita is the asymmetrical in size cells of the initial colors, that is the ACSP (Assymetrical Cell Structure Panel) technology. It is known that in the control of the balance of white the initial colors include with the different weighting coefficients. In the panels with the equal cells this circumstance has to be taking into account by the according impulse correction. Matsushita offered another: the correction by the cell size (Toshio Wakahara. Matsushita PDPs offer high contrast, compare well with CRTs, JEY, 2000, 112). We'll add also that by that scheme the blue color cell happened to be the biggest, what allows it to light the neighbors easily by the ultraviolet and that gives the nice blue tint to the screen. But to say the truth the production of the panels with three sizes of the cells becomes more complicated, but that is another story.

In 1998 Fujitsu, one of the pillars of the panel display devices, developed the AliS (Alternate Lighting of Surface) technology. The developers of the PDP are usually faced with the problem of the increase of the resolution at the given screen parameters. The direct way of the increase of the amount of pixels is connected with the necessity of the cell size decrease and the plasma volumes as well, and at the end the pixels brightness. Other problems appear as well. For the solution of the mentioned problem of the increase of the resolution for the PDPs with the small screens the technology of the double scanning was developed. The 'alternative' happened to be in the interlaced fields' interchange! But the company did not achieve the target. More over, with the increase of the reproduced clearness it succeeded in the image brightness. The LCD and PDP TV sets push out the kinescope TV sets from the everyday life more and more intensively. These processes somehow touched the professional area of the television system. The large triad of the CRT, LCD and PDP sorts out the relationships and divides the spheres of influence, the outcast is determined. This is CRT. And what is in a perspective? Is it possible that the LCD and PDP perfect in everything will become the leaders in the television sphere? Where are the opponents?

The answer can be searched for along time: why does the all-powerful contemporary science that created so much, couldn't offer something newer than the CRT, LCD and PDP by the new millenium? It is, of course, known in what is the complicity of the task. The display devices are the joint of the two information channels of the different spaces. The information is received by the one-dimensional connection channel and reproduces by the two-dimensional image channel.

Till today directly or indirectly, but the broach or its sister commutation provides the switch between the two spaces. It is difficult to expect the overturn in the reflection case, till the status quo remains. The informational techniques is has been waiting for the appearance of the optical processors processing the information by arrays, but not bit after bit as now, for a long time. There will appear such a two-dimensional processor and there will be the new reflection principles. In the nest year it definitely won't happen.

In that part of the review we provide the free table of the last models of the plasma panels of the leading companies.

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