Název práce:
Displeje na principu kapalných krystalů
Autor:
Dana Javůrková
Datum:
20. 12. 2002
Seznam kapitol: 1) 2) 3) 4) 5) 6) 7) 8)
Úvod Charakteristika Historie tekutých krystalů Princip, technologie LCD Vývoj a struktura LCD Použití LCD a článek o virtuální realitě Závěr Odkaz na internetové adresy
Úvod Displeje z kapalných krystalů jsou řízeny aplikací el. napětí, díky němuž se kapalný krystal orientuje do správného směru, tak aby jím mohlo procházet světlo.Kapalné krystaly jsou protáhlé organické molekuly, které mají vlastnosti částečně kapalných a částečně pevných látek. Byly objeveny na konci 19. století, využívat se začlaly teprve před třiceti lety. Nejdříve se z nich vyráběly displeje pro kapesní kalkulačky, dnes se využívají i pro zobrazování na počítačových monitorech. V elektronice našly široké uplatnění, protože nabízí řadu výhod. V posledních letech bylo vyvinuto několik typů LCD displejů. Je vysoce pravděpodobné, že LCD monitory v nejbližší době vytlačí klasické monitory z trhu.
Charakteristika HowLCDsWork Introduction to How LCDs Work, Liquid Crystals, Light and Electricity, Building a Simple LCD, Backlit vs. Reflective, Common Plane, Passive Matrix and Active Matrix, Color and the
Future, Lots More Information! You probably use items containing an LCD (liquid crystal display) every day. They are all around us -- in laptop computers, digital clocks and watches, microwave ovens, CD players and many other electronic devices. LCDs are common because they offer some real advantages over other display technologies. They are thinner and lighter and draw much less power than cathode ray tubes (CRTs), for example. But just what are these things called liquid crystals? The name "liquid crystal" sounds like a contradiction. We think of a crystal as a solid material like quartz, usually as hard as rock, and a
liquid is obviously different. A liquid crystal is an intermediary substance between a liquid and solid state of matter How could any material combine the two? We learned in school that there are three common states of matter: solid, liquid or gaseous. Solids act the way they do because their molecules always point the same way and stay in the same position with respect to one another. The molecules in liquids are just the opposite: They can point in any direction and move anywhere in the liquid. But there are some substances that can exist in an odd state that is sort of like a liquid and sort of like a solid. When they are in this state, their molecules tend to point the same way, like the molecules in a solid, but also move around to different positions, like the molecules in a liquid. This means that liquid crystals are neither a solid nor a liquid. That's how they ended up with their seemingly contradictory name. Abbreviation of liquid crystal display, a type of display used in digital watches and many portable computers. LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light. Monochrome LCD images usually appear as blue or dark gray images on top of a grayishwhite background. Color LCD displays use two basic techniques for producing color: Passive matrix is the less expensive of the two technologies. The other technology, called thin film transistor (TFT) or active-matrix, produces color images that are as sharp as traditional CRT displays, but the technology is expensive. Recent passive-matrix displays using new CSTN and DSTN technologies produce sharp colors rivaling active-matrix displays. So, do liquid crystals act like solids or liquids or something else? It turns out that liquid crystals are closer to a liquid state than a solid. It takes a fair amount of heat to change a suitable substance from a solid into a liquid crystal, and it only takes a little more heat to turn that same liquid crystal into a real liquid. This explains why liquid crystals are very sensitive to temperature and why they are used to make thermometers and mood rings. It also explains why a laptop computer's display may act funny in cold weather or during a hot day at the beach!
Historie kapalných krystalů Today, LCDs are everywhere we look, but they didn't sprout up overnight. It took a long time to get from the discovery of liquid crystals to the multitude of LCD applications we now enjoy. Liquid crystals were first discovered in 1888, by Austrian botanist Friedrich Reinitzer. Reinitzer observed that when he melted a curious cholesterol-like substance (cholesteryl benzoate), it first became a cloudy liquid and then cleared up as its temperature rose. Upon cooling, the liquid turned blue before finally crystallizing. Liquid crystal is a term that indicates the status of a substance that is neither solid nor liquid, e.g. soapy water. In 1963, Williams, while working for RCA discovered that the way light passes through liquid crystal changes when it is stimulated by an electrical charge. Eighty years passed before RCA made the first experimental LCD in 1968. Heilmeyer and his colleagues made a display prototype that applied this concept. This prototype's success marked the beginning of modern liquid crystal display (LCD) technology. In the beginning, liquid crystals were initially too unstable to use as a material for manufacturing display units, creating several merchandising problems for LCD technology until a professor of the University of Hull in the U.K. made a scientific breakthrough when he discovered a stable liquid crystal material (biphenyl). Sharp further refined LCD technology, and in 1973 introduced the EL-8025, the world's first electronic calculator featuring an LCD display. The core technology behind the development of the the EL8025 still forms the basis all current LCD products. Since then, LCD manufacturers have steadily developed ingenious variations and improvements on the technology, taking the LCD to amazing levels of technical complexity. And there is every indication that we will continue to enjoy new LCD developments in the future!
Princip a technologie LCD LCD Technology LCDs, Liquid Crystal Displays, are a passive display technology. (This means they do not emit light) Instead, they manipulate the ambient light in the environment to display images. This technology requires very little power to operate which has made LCDs "the preferred technology" especially when compact size and low power consumption are paramount. LCDs consist of two pieces of glass with electrodes printed on the inside. On each glass surface an alignment layer twists the liquid crystal material in a "twisted" or helical pattern. Polarizers are used on the outside front and rear surfaces. Twisted Nematic is the most common type of liquid crystal used in LCDs today. This organic substance has both a liquid form and a crystal molecular structure. Normally, the rod-shaped molecules are in a parallel array, and an electric field can be used to control the molecules. Many advances in Twisted Nematic LCDs have been produced. Super Twisted Nematic liquid crystal material offers a higher twist angle (>=200° vs. 90°) that provides higher contrast and a better viewing angle. A disadvantage is that the the background color shifts to yellow-green and the character color shifts to blue. (This is called the birefringence effect.) However, by using a special filter, the background color can be changed to a gray. Film Super Twisted Nematic displays are the most recent advance that has been made. Film Super Twisted Nematic displays add a retardation film to the Super Twisted Nematic display that compensates for the color added by the birefringence effect. This retardation film allows a black and white display to be produced. When the LCD is 'OFF,' no voltage is applied to the electrodes, and light passes through the LCD.When it is 'ON,' voltage is applied and the LC molecules align themselves in the direction of the electric field. This causes the LC to be out of phase with the light, creating a dark area on the LCD. By selectively applying voltage to the electrodes, a variety of patterns can be achieved. Our LCD industrial flatpanel monitors are available in the following mechanical configurations (chassis mount, rackmount, panel mount, wall/arm mount, and rugged tabletop) and in a variety of sizes (6.4", 8.4", 10.4", 12.1", 15.1", 17.0", 18.1", 20.1" and 21.3"). Liquid Crystal Types Most liquid crystal molecules are rod-shaped and are broadly categorized as either thermotropic or lyotropic Thermotropic liquid crystals will react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Thermotropic liquid crystals are either isotropic or nematic. The key difference is that the molecules in isotropic liquid crystal substances are random in their arrangement, while nematics have a definite order or pattern. The orientation of the molecules in the nematic phase is based on the director. The director can be anything from a magnetic field to a surface that has microscopic grooves in it. In the nematic phase, liquid crystals can be further classified by the way molecules orient themselves in respect to one another. Smectic, the most common arrangement, creates layers of molecules. There are many variations of the smectic phase, such as smectic C, in which the molecules in each layer tilt at an angle from the previous layer. Another common phase is chlorestic, also known as chiral nematic. In this phase, the molecules twist slightly from one layer to the next, resulting in a spiral formation. Just as there are many varieties of solids and liquids, there is also a variety of liquid crystal substances. Depending on the temperature and particular nature of a substance, liquid crystals can be in one of several distinct phases (see sidebar). In this article, we will discuss liquid crystals in the nematic phase, the liquid crystals that make LCDs possible.
One feature of liquid crystals is that they're affected by electric current. A particular sort of nematic liquid crystal, called twisted nematics, (TN), is naturally twisted. Applying an electric current to these liquid crystals will untwist them to varying degrees, depending on the current's voltage. LCDs use these liquid crystals because they react predictably to electric current in such a way as to control light passage. Ferroelectric liquid crystals (FLCs) use liquid crystal substances that have chiral molecules in a smectic C type of arrangement because the spiral nature of these molecules allows the microsecond switching response time that make FLCs particularly suited to advanced displays. Surface-stabilized ferroelectric liquid crystals (SSFLCs) apply controlled pressure through the use of a glass plate, suppressing the spiral of the molecules to make the switching even more rapid. Princip In this section, we will explain everything ranging from the properties of liquid crystal molecules to the basic principle of display technology by using TN type liquid crystals as an example. The parallel arrangement of liquid crystal molecules along grooves. When coming into contact with grooved surface in a fixed direction, liquid crystal molecules line up parallelly along the grooves.Natural state:
Molecules are arranged in a loosely ordered fashion with their long axes parallel.
Molecules When coming into contact with a line up parallel along grooves. finely grooved surface (alignment layer).
When liquid crystals are sandwiched between upper and lower plates, they line-up with grooves pointing in directions 'a' and 'b,' respectively The molecules along the upper plate point in direction 'a' and those along the lower plate in direction 'b,' thus forcing the liquid crystals into a twisted structural arrangement./ (figure shows a 90-degree twist) (TN type liquid crystal)
Light travels through the spacing of the molecular arrangement. The light also "twists" as it passes through the twisted liquid crystals
Light passes through liquid crystals, following the direction in which the molecules are arranged. When the molecule arrangement is twisted 90 degrees as shown in the figure, the light also twists 90 degrees as it passes through the liquid crystals. Light bends 90 degrees as it follows the twist of the molecules Molecules rearrange themselves when voltage is applied. When voltage is applied to the liquid crystal structure, the twisted light passes straight through. The molecules in liquid crystals are easily rearranged by applying voltage or another external force. When voltage is applied, molecules rearrange themselves vertically (along with the electric field) and light passes straight through along the arrangement of molecules. Blocking light with two polarizing filters When voltage is applied to a combination of two polarizing filters and twisted liquid crystal, it becomes a LCD display. Light passes when two polarizing filters are arranged with polarizing axes as shown above, left. Light is blocked when two polarizing filters are arranged with polarizing axes as shown above, right.
TN type LCDs A combination of polarizing filters and twisted liquid crystal creates a liquid crystal display. When two polarizing filters are arranged along perpendicular polarizing axes, light entering from above is re-directed 90 degrees along the helix arrangement of the liquid crystal molecules so that it passes through the lower filter. When voltage is applied, the liquid crystal molecules straighten out of their helix pattern and stop redirecting the angle of the light, thereby preventing light from passing through the lower filter. This figure depicts the principle behind typical twisted nematic (TN) liquid crystal displays. In a TN type LCD, liquid crystals in which the molecules form a 90-degree twisted helix, are sandwiched between two polarizing filters. When no voltage is applied, light passes; when voltage is applied, light is blocked and the screen appears black. In other words, the voltage acts as a trigger causing the liquid crystals to function like the shutter of a camera. Systémy displejů Displaying letters, numbers and graphics are based on the following three display methods:
1. Segment systém Long display units are arranged to form a figure '8' to display numbers.
2. Dot matrix system (character display) Display units are arranged in rows and columns to form characters.
3. Dot matrix system (graphics display) Display units are arranged in rows and columns to depict graphics.
Princip barevných diplejů A color display is made possible by placing color filters over each display unit. In dot matrix systems, red, green and blue dots are obtained through the use of filters for each of the three primary colors red (R), green (G) and blue (B). A variety of colors can then be expressed by combining them. Konfigurace displejů The light passing through the liquid crystals is merely natural or artificial ambient light. The configuration of the display is categorized by the relative position of the light source. There are three types: 1) Transmissive type (LCD TV) 2) Reflective type (LCD calculator, watch) 3) Projection type (LCD projection)
Struktura LCD Next is a brief description of the structure, liquid crystal materials and production process of a simple matrix LCD. LCD structure Sandwiched structure
Color LCDs have a structure in which their components are formed into a sandwich-like arrangement. 1. Polarizing filter. This controls the light entering and leaving. 2. Glass substráte. This stops the filtering of electricity from electrodes 3. Transparent electrodes. These electrodes drive the LCD. A highly transparent material is used that will not interfere with the quality of the image's integrity. 4. Alignment layer. Film is used to align the molecules in a fixed direction. 5. Liquid crystals 6. Spacer. Maintains a uniform space between the glass plates. 7. Color filter. Color is expressed through the use of R, G and B filters. 8. Backlighting. The display is lit from behind to make the screen brighter. In some types of monochrome LCDs, a mirror is used in place of backlighting so the display can be seen with ambient light.
Vývoj LCD LCD technology has come a long way in the last several years, resulting in a steady stream of new products. LCD Evolution
Improved display performance The first displays were segment types that could only display numbers, then these were followed by dot-matrix systems capable of displaying characters and graphics. Displays later evolved from monochrome to color, from still images to moving images, and from small to large screens. The evolution of three LCD technologies 1. Drive systéme 2. LCD types 4. Peripheral technologies
The Evolution of Drive Systems Static drive system
Dynamic drive system
Example showing four upper electrodes and two lower electrodes. An upper electrode is connected The display segment to be shown is selected by segment to be to each display segment. shown is selected by combinations of upper and lower electrodes. From static to dynamic drives A drive system 'drives' the LCD by applying voltage to specific electrodes. In the early days of LCD development, a segment systems used a static drive system in which each segment was driven separately. The number of terminals required in this system increases with the number of display units, making it unsuitable for use with large screens. The development of a dynamic drive made it possible to drive displays with fewer terminals. Simple and active matrix drives Today, static drives are now rarely used. The most common dynamic drive systems in use today are active matrix drives and simple matrix drives. Active matrix drives are used for TVs and other moving picture applications which require high picture quality and a fast response. Simple matrix drives are mostly used in calculators, word processors, personal computers and other still image applications.
Struktura Simple/Active Matrix řídících systémů Structure of simple matrix drive systém
The X electrodes are laid on the lower substrate of the liquid crystal cell, and the Y electrodes are laid on the upper substráte. Electrical signals are applied to the X and Y conductors with the proper timing to select the target pixels. The structure of active matrix drive systems (TFT)
In active matrix LCDs, switching transistors (TFTs) or diodes are attached to each pixel to switch each one on or off. X and Y electrodes are formed on the same substrate as TFT (or diode) arrays. The switching signals are applied to the X electrodes. Video signals are then applied to the Y electrodes. Major types of LCDs TN Structure Color
Features
Problems or advantages Main applications
Twists nematic crystals 90 degrees Black/white
Low power consumption Thin, lightweight Low cost
Cannot handle a large capacity Calculators, electronic organizers
STN Twists nematic crystal about 260 degrees (opposing twist directions)
TSTN Replaces DSTN compensation cell with plastic film
Yellow-green/dark blue
Black/white, multicolor
Large capacity display Thin, lightweight Low power consumption High contrast
Large capacity display Thin, lightweight Low power consumption Color display High contrast
Black/white display not possible (therefore, color display not possible) Word processors (monocolor)
High contrast and high speed Word processors, laptop computers
From TN to STN, TSTN, and FSTN The very first types of LCDs were called DSM (dynamic scattering mode), but TN (twisted nematic) has become the standard today. Almost all active matrix drive displays use TN type LCDs,
and numerous types of active elements are being developed. The use of TN type LCDs in simple matrix drive displays causes the contrast to drop as the number of scan lines of the image displayed is increased. To compensate for this, new types of LCDs are being researched and developed. Advances in LCD R&D have already led to the development of STN (super twisted nematic) type LCDs, which offer high contrast, even on large screens; and TSTN (triple STN) and FSTN (film STN) LCDs, which feature a lightweight and thin body design that are optimal for large black-andwhite LCDs and precise color imaging when equipped with a color filter. Conceptual diagrams of major LCD types Twisted Nematic (TN) Type
Contrast tends to drop when used with large screens.
Molecules twisted 90 degrees. Super Twisted Nematic (STN) Type
Good rise characteristic for a high contrast display
180 degrees to 260 degrees twist. Colored yellow-green and blue Triple Super Twisted Nematic (TSTN) Type A high polymer, double refraction film is used to create black-andwhite LCDs of exceptional quality. The single-layer compensation film is called FSTN (Film Super Twisted Nematic). A compensation film is placed above and below the operating cell. TFT structural configuration
TFT structure is composed of three electrodes--X,Y and Z--which act as switching transistors. MIM structural configuration
This is structurally identical to the simple matrix system, but has only the two X and Y electrodes. A diode with a metallic-insulated metal structure is sandwiched between the two terminals. The diode performs the switching function in place of the transistor, but it is slow. Active elements The following types of active elements are used in active matrix systems: the three-terminal element, typified by thin-film transistors (TFTs) including amorphous Si-TFTs, high-temperature polycrystal Si-TFTs, and low-temperature polycrystal Si-TFTs; the two-terminal element, of which metal-insulator-metal (MIM) is typical; and plasma and address variations. The structure of the three-terminal element offers superior switching performance. TN is the most commonly used LCD structure. Summary--comparing various types of LCDs Below is a list of the differences between drive systems, LCD types and active elements, together with their respective features. As can be seen from the table, an LCD with an active matrix system, TN type LCDs, and TFT LCDs offer the best overall performance. System
Structure
Features
Problems
Picture quality drops when X and Y electrodes are laid Simple production the number of wires is Simple out in a vertical and Superior cost incresed matrix drive horizontal lattice advantages Halftone response speed An insulator which performs switching is sandwiched MIM between the X and Y terminals Active matrix drive
Applications Primarily still images such as in the electronic organizers, word processors and personal computers
Picture quality is between that of simple matrix and Word processors, TFT active matrix drive displays personal computers, Production ease and cost are both between those of TVs simple matrix and TFT active matrix drive displays
High contrast and high picture quality A silicon thin-film regardless of semiconductor which number of TFT performs switching between conductors the X and Y terminals Permits halftone display Superior response
High cost
TVs, projection displays and other moving picture applications
Building a Simple LCD There's far more to building an LCD than simply creating a sheet of liquid crystals. The combination of four facts makes LCDs possible: • • • •
Light can be polarized. (See How Sunglasses Work for some fascinating information on polarization!) Liquid crystals can transmit and change polarized light. The structure of liquid crystals can be changed by electric current. There are transparent substances that can conduct electricity. An LCD is a device that uses these four facts in a surprising way!
To create an LCD, you take two pieces of polarized glass. A special polymer that creates microscopic grooves in the surface is rubbed on the side of the glass that does not have the polarizing film on it. The grooves must be in the same direction as the polarizing film. You then add a coating of nematic liquid crystals to one of the filters. The grooves will cause the first layer of molecules to align with the filter's orientation. Then add the second piece of glass with the polarizing film at a right angle to the first piece. Each successive layer of TN molecules will gradually twist until the uppermost layer is at a 90-degree angle to the bottom, matching the polarized glass filters. As light strikes the first filter, it is polarized. The molecules in each layer then guide the light they receive to the next layer. As the light passes through the liquid crystal layers, the molecules also change the light's plane of vibration to match their own angle. When the light reaches the far side of the liquid crystal substance, it vibrates at the same angle as the final layer of molecules. If the final layer is matched up with the second polarized glass filter, then the light will pass through.
If we apply an electric charge to liquid crystal molecules, they untwist! When they straighten out, they change the angle of the light passing through them so that it no longer matches the angle of the top polarizing filter. Consequently, no light can pass through that area of the LCD, which makes that area darker than the surrounding areas. Building a simple LCD is easier than you think. Your start with the sandwich of glass and liquid crystals described above and add two transparent electrodes to it. For example, imagine that you want to create the simplest possible LCD with just a single rectangular electrode on it. The layers would look like this: The LCD needed to do this job is very basic. It has a mirror (A) in back, which makes it reflective. Then, we add a piece of glass (B) with a polarizing film on the bottom side, and a common electrode plane (C) made of indium-tin oxide on top. A common electrode plane covers the entire area of the LCD. Above that is the layer of liquid crystal substance (D). Next comes another piece of glass (E) with an electrode in the shape of the rectangle on the bottom and, on top, another polarizing film (F), at a right angle to the first one. The electrode is hooked up to a power source like a battery. When there is no current, light entering through the front of the LCD will simply hit the mirror and bounce right back out. But when the battery supplies current to the electrodes, the liquid crystals between the common-plane electrode and the electrode shaped like a rectangle untwist and block the light in that region from passing through. That makes the LCD show the rectangle as a black area.
Backlit vs. Reflective Note that our simple LCD required an external light source. Liquid crystal materials emit no light of their own. Small and inexpensive LCDs are often reflective, which means to display anything they must reflect light from external light sources. Look at an LCD watch: The numbers appear where small electrodes charge the liquid crystals and make the layers untwist so that light is not transmitting through the polarized film. Most computer displays are lit with built-in fluorescent tubes above, beside and sometimes behind the LCD. A white diffusion panel behind the LCD redirects and scatters the light evenly to ensure a uniform display. On its way through filters, liquid crystal layers and electrode layers, a lot of this light is lost -- often more than half! In our example, we had a common electrode plane and a single electrode bar that controlled which liquid crystals responded to an electric charge. If you take the layer that contains the single electrode and add a few more, you can begin to build more sophisticated displays. Common Plane, Passive Matrix and Active Matrix Common-plane-based LCDs are good for simple displays that need to show the same information over and over again. Watches and microwave timers fall into this category. Although the hexagonal bar shape illustrated previously is the most common form of electrode arrangement in such devices, almost any shape is possible. Just take a look at some inexpensive handheld games: Playing cards, aliens, fish and slot machines are just some of the electrode shapes you'll see! There are two main types of LCDs used in computers, passive matrix and active matrix. Passive-matrix LCDs use a simple grid to supply the charge to a particular pixel on the display. Creating the grid is quite a process! It starts with two glass layers called substrates. One substrate is given columns and the other is given rows made from a transparent conductive material. This is usually indiumtin oxide. The rows or columns are connected to integrated circuits that control when a charge is sent down a particular column or row. The liquid crystal material is sandwiched between the two glass substrates, and a polarizing film is added to the outer side of each substrate. To turn on a pixel, the integrated circuit sends a charge down the correct column of one substrate and a ground activated on the correct row of the other. The row and column intersect at the designated pixel, and that delivers the voltage to untwist the liquid crystals at that pixel.
The simplicity of the passive-matrix system is beautiful, but it has significant drawbacks, notably slow response time and imprecise voltage control. Response time refers to the LCD's ability to refresh the image displayed. The easiest way to observe slow response time in a passivematrix LCD is to move the mouse pointer quickly from one side of the screen to the other. You will
notice a series of "ghosts" following the pointer. Imprecise voltage control hinders the passive matrix's ability to influence only one pixel at a time. When voltage is applied to untwist one pixel, the pixels around it also partially untwist, which makes images appear fuzzy and lacking in contrast. Active-matrix LCDs depend on thin film transistors (TFT). Basically, TFTs are tiny switching transistors and capacitors. They are arranged in a matrix on a glass substrate. To address a particular pixel, the proper row is switched on, and then a charge is sent down the correct column. Since all of the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor is able to hold the charge until the next refresh cycle. And if we carefully control the amount of voltage supplied to a crystal, we can make it untwist only enough to allow some light through. By doing this in very exact, very small increments, LCDs can create a gray scale. Most displays today offer 256 levels of brightness per pixel. Color and the Future An LCD that can show colors must have three subpixels with red, green and blue color filters to create each color pixel. Through the careful control and variation of the voltage applied, the intensity of each subpixel can range over 256 shades. Combining the subpixels produces a possible palette of 16.8 million colors (256 shades of red x 256 shades of green x 256 shades of blue), as shown below. These color displays take an enormous number of transistors. For example, a typical laptop computer supports resolutions up to 1,024x768. If we multiply 1,024 columns by 768 rows by 3 subpixels, we get 2,359,296 transistors etched onto the glass! If there is a problem with any of these transistors, it creates a "bad pixel" on the display. Most active matrix displays have a few bad pixels scattered across the screen.
LCD technology is constantly evolving. LCDs today employ several variations of liquid crystal technology, including super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC). Display size is limited by the quality-control problems faced by manufacturers. Simply put, to increase display size, manufacturers must add more pixels and transistors. As they increase the number of pixels and transistors, they also increase the chance of including a bad transistor in a display. Manufacturers of existing large LCDs often reject about 40 percent of the panels that come off the assembly line. The level of rejection directly affects LCD price since the sales of the good LCDs must cover the cost of manufacturing both the good and bad ones. Only advances in manufacturing can lead to affordable displays in bigger sizes. How is the LCD in a laptop computer so bright? Most computer Liquid Crystal Display (LCD) panels are lit with built-in fluorescent tubes above, beside and sometimes behind the LCD. A white diffusion panel behind the LCD redirects and scatters the light evenly to ensure a uniform display. This is known as a backlight. A fluorescent light is most often a long straight glass tube that produces white light. Inside the glass tube there is a low-
pressure mercury vapor. When ionized, mercury vapor emits ultraviolet light. Human eyes are not sensitive to ultraviolet light (although human skin is). The inside of a fluorescent light is coated with phosphor. Phosphor is a substance that can accept energy in one form and emit the energy in the form of visible light. For example, energy from a high-speed electron in a TV tube is absorbed by the phosphors that make up the pixels. The light we see from a fluorescent tube is the light given off by the phosphor coating the inside of the tube. The phosphor fluoresces when energized, hence the name.(Compare the size of this fluorescent tube from a laptop computer to the pencil beside it and you see how tiny it is.) A typical laptop display uses a tiny Cold Cathode Fluorescent Lamp (CCFL) for the backlight. One of these small tubes is able to provide a bright white light source that can be diffused by the panel behind the LCD. In addition to providing ample light, CCFLs do not rise far above the ambient temperature. This makes them ideal for LCD panels since the light source is in close proximity to other components that could be ruined by excessive heat. One amazing thing about these lamps is their incredible size. They are very thin and the board that drives the lamp is very small as well. However, it is not that hard to break them, which is why your display may go dark if you drop your laptop.
Aplikace Applications for liquid crystal displays now extend beyond calculators and digital watches to countless other products, including word processors, televisions and even video systems on trains. Personal Information Tool (for Japanese market)
Keyboard-enhanced Personal Information Tool (for international markets) Personal Information ToolsŃprogress in portability and operability LCD Pad Wiz, one of Sharp's cutting-edge personal information tools, has a compact and lightweight body designed to neatly fit into a shirt pocket. With an intelligent handwritten character recognition function, users can quickly input and interactively share data via telephone lines. Wiz allows users to make full use of the data as if they had written the information down in a pocketbook. The Personal Information Tool enables data to be collected and transmitted by a PC data link, electronic mail, facsimiles, or from pay phones and portable phones. These and other personal information tools will soon be equipped with color LCD monitors to substantially expand and upgrade information handling and management.
LCDs in everyday life LCDs are finding a growing variety of applications in televisions, word processors, personal computers, and in other electronic office equipment products. LCDs are widely used in imaging and information systems that are commonly found in Japanese railway systems and other modes of transportation.
The continuing progress of LCDs The greatly expanded use of LCDs is the result of recent significant breakthroughs made in the following four areas of LCD technology: advancing beyond alphanumeric to graphic capabilities advancing beyond monochrome displays to color advancing beyond only still images to moving Picture advancing being small screen displays to now using large screens . On The Cutting Edge of Display Technology Until very recently, most AV and data communications devices used cathode ray tube (CRTs) monitors as their main display device. CRTs, however, require high voltage for the emission and angle control of the electron beams, and it is difficult to slim-down the size of CRT units. Flat panel display technology is the perfect answer to demands for more compact displays with greater energy efficiency and diversity. From CRTs to flat panel displays Flat panel displays are being developed to realize 1) a thinner unit and 2) low voltage operation and low power consumption--objectives not easily achieved with CRTs. There are a number of distinct systems which differ by the types of materials and the display method they use. LCD (liquid crystal display) PDP (plasma display) LED (light emitting diode) EL (electroluminescent) panel VFD (vacuum fluorescent display) DMD (digital micromirror device): projection type FED (field emission display) LCDs--the display of choice Of all these systems, the liquid crystal display is considered to be the most promising. In addition to being thin and lightweight, these displays run on voltages so low they can be driven directly by an LSI. And since they consume low power, they can run for long periods on batteries. Additional advantages over other types of flat panel display include: adaptability to full color low cost large potential for technological development The world's first large-size LCD offering images as clear and crisp as a CRT In the past, LCD picture quality was considered inferior to that of CRTs, and creating LCDs in sizes greater than 10 inches were not though possible. This changed dramatically in 1988 when a remarkable prototype with the following features was introduced: 14" screen (the largest LCD screen to date) 27 mm thick (about 1/13 that of 14" CRTs) 1.8 kg (about 1/4 that of 14" CRTs) Picture quality comparable to a CRT
The secret to large screen, high-resolution LCD imaging "active matrix" and "TFT" The active matrix system is one configurational method of driving an LCD. It offers quick responsiveness to moving pictures and high picture quality. This 28-inch LCD screen offers 307,200 pixel (640 x 480 resolution) and RGB compatibility enabling high-definition 921,600-dot image reproduction. A TFT (thin film transistor) is applied to each pixel, ensuring concise control to create high-contrast full-color display images. The secret to a beautiful picture "Normally white" With products that employ this technology, the screen is normally white when no voltage is applied. The use of a white screen creates darker colors during operation, so better contrast is achieved than in other products in which screens are normally black when no voltage is applied. Because of a high contrast shutter function, beautiful multicolor images can be reproduced by superimposing RGB color fitters. Screen size:
28 inches (704 mm)
Number of pixels:
640 x 480 RGB dots
Pitch of pixels:
0.88 x 0.88 mm
Number of colors:
16.7 million colors
Outside dimensions:
633(W) x 510(H) x 37(D) mm
Power consumption:
Approx. 100W
Contrast:
100:1 or more
Brightness:
150 cd/cm2
Weight:
18 kg
Main product Multitask displays for PCs, information panels, presentation screens, functions: monitor displays for conferences, wall-mount TVs, etc.
LCD Display TVs (for Japanese market) Thin profile and lightweight designs with amazingly high picture quality Both the 10.4-inch and 8.4-inch models project clear and crisp images in an astounding 920,000 pixel resolution. Low-reflectivity TFT LCD panels are used to reduce the reflection of external light, thereby ensuring easy-on-the-eye image viewing. Advanced LCD technology has made it possible to design the 10.4-inch LCD Display TV in an ultra-slim and lightweight body with a weight of 2.3 kg an a monitor profile of just 47 mm. The LCD Display TVs can be placed on the top of a desk or table, or the kitchen countertop, thus matching a wide range of viewing styles.
28-Inch TFT Full-Color LCD Display
Car Navigation LCD TV
The Car Navigation LCD TV goes anywhere The LCD Car Navigation System features a quick-release method which allows the monitor to be detached from the GPS unit and the connector. When you arrive at a destination, you can take the monitor out of the car and use it as a portable LCD television for maximum mobility. The car navigator incorporates low-reflectivity LCD panels and a high-brightness backlight, ensuring easyon-the-viewing excitement even in a bright car interior or outdoors in the day time. Apart from delivering clear and crisp TV broadcasts, the Car Navigation System also provides high-definition displays of automobile-navigation maps. LCD PanelVision TV
LCD technology--expanding super large-screen visual excitement The rear LCD projection system of the LCD PanelVision TV delivers bright, vivid-color and easy-on-the-eyes viewing on a large screen that captures all the excitement of television entertainment. Equipped with a super-large 43-inch screen, the TV weighs approximately 41 kg and has a space-saving width of only 38.5 cm. LCD Video Projector
LCD Rear Projection System Configuration Lamp: newly developed high-brightness metal halide lamp M1-M3: Full-reflection mirrors Filter: Ultraviolet-ray filter DM1-DM4: Dichroic mirrors C1-C3: Condenser lenses Beautifully reproduce detailed imagesĐeven in a brightly lit room Delivering a 4,000-lux screen brightness four times as bright as that of conventional models, the LCD video projector offers unsurpassed high-contrast quality images. There are three LCD panels built in the projector, each of which lets red, green or blue light pass. These three basic colors then converge to form colorful, animated pictures.
Hi-Vision LCD Projector The odds-on winner of the HDTV era delivers high-definition pictures with high-pixel density This compact, lightweight Hi-Vision LCD Projector utilizes two-inch polysilicon TFT panels that reproduce Hi-Vision images with a high-definition quality of 1,125 scanning linesŃdouble the number of conventional models, and a 16:9 screen ratio compared with the 4:3 ratio of most other projectors. Images are projected onto a super large-screen in an adjustable size ranging from 55 to 200 inches. The main features of the compact, lightweight Hi-Vision LCD Projector include: The utilization of three high-definition two-inch polysilicon TFT LCD panels (one with 1.31 million pixels) for the Hi-Vision system which reproduces the three RGB basic colors The realization of 400:1 ratio high-contrast images. Enhance brightness by about 40% over most other conventional LCD video projectors by a high-transparency LCD panel.
LCD Miracle Screen System From show window to screen in a flash The LCD Miracle Screen combines the LCD video projector and Instant Photosensitive Glass (LCD) which becomes opaque or transparent by turning the power on and off. Instant Photosensitive Glass is ordinarily a transparent show window, but when the power is turned off, it becomes an opaque screen on which LCD images can be projected. The Miracle Screen System can be used in various ways for window displays and special events. TFT Color LCD Notebook Computers
DSTN Color LCD Notebook Computer (for Japanese market) TFT LCD configuration In AV displays, full color is reproduced by arranging RGB pixels in a delta configuration. In office equipment displays, the sharp contrast between graphics and characters is produced using a stripe configuration of RGB pixels. For AV equipment: For office equipment: Delta configuration--full color Stripe configuration--multicolor
Thin and lightweight with low power consumption Sharp TFT LCD Modules feature thin profiles, light weight and low power consumption. Now setting new standards in notebook-size PCs, they deliver bright, clear images of the highest quality, making them ideal displays for the multimedia notebook PCs of the future. Through the
development of original technology, Sharp has successfully designed TFT color LCDs with a super high-aperture ratio of 81% compared to the 47% ratio of conventional 10.4-inch SVGA models, thereby offering substantially reduced power consumption and enhanced picture quality. This advanced proprietary technology is applied to the production of Sharp's TFT LCD modules (the 10.4-inch S-VGA, 11.3-inch SVGA, 12.1-inch XGA displays) for use in multimedia-compatible notebook PCs. 1. VGA: Offered in standard PCs with 640 x 480 RGB pixel resolution for displaying PC-generated images. 2. SVGA: With 800 x 600 RGB pixel resolution, PC-generated images are displayed with a display capacity 1.6 times larger than VGA specifications. 3. XGA: 1024 x 768 RGB pixel resolution for displaying images with a display capacity 2.6 times larger than VGA specifications. STN Color LCD Displays
Japanese Color Word Processor (for Japanese market) Convenient, fun, and user-friendly vivid-color reproduction Sharp's Color Japanese Word Processor is equipped with an OCR (optical character reader) feature that allows typed characters from newspapers and magazines to be inputted as text data. It also allows video images and photographs to be read in and processed for graphic layout use, as well as pen-based input and editing supported by enhanced handwritten character and graphic recognition functions. Japanese Color Word Processor is also equipped with a color LCD monitor which allows users to craft documents in stunning color, improving visibility, fun, and ease of use.
STN LCD Displays
Large-Screen Color STN LCD 17.7-inch XGA Color LCDs High picture quality with a simple matrix system An LCD has been introduced that uses the simple matrix system, which is ideal for still images, to provide picture quality that is sufficiently high for office and image data processing equipment. Its features include: Low cost Multicolor (16.7 million colors) Adaptable to large screens Applicable to a wide range of products including personal information devices New color LCD reduces on-screen shadow and increases picture quality Thanks to a new driver technique, Sharp has been able to create a new level of LCD excitement by substantially reducing the on-screen shadow. Sharp is currently working on advancing this breakthrough to improve the LCD response rate in order to better process high-speed moving images. Some of the new driver's features include: A higher-quality LCD picture, which is achieved by reducing the display shadow through the development of a new LCD driver and peripheral circuitry that corrects and regulates changes in the electrical voltage feeding the liquid crystal matrix. Wide-angle viewing, which is achieved by adding new optical film as well as the conventional phase difference plate. A process for giving all the cells a uniform thickness. A process for making the unit thinner and lighter. DMGH-Method Reflective Color LCDs
A four-color, easy-on-the-eyes LCD with low power-consumption that achieves an amazing level of brightness without a backlight DMGH (Double Metal Guest Host)ŃMethod Reflective Color LCDs are one of the types of the active-matrix systems that use diodes for switching. The following major features are offered by DMGH reflective LCDs: 1. Bright, easy-on-the-eyes screen without a backlight:
Guest Host LCDs eliminate the need for deflecting plates. 2. Four-color display including easy-to-read "paper white" background color: Cyan and red complementary-color micro-filters enable four-color display in green, red, white, and black. 3.Low power consumption: The unit consumes only 60 mW, approximately one-third the amount of power needed by conventional LCDs equipped with a backlight system (on a 6-inch office equipment unit with 1.8 W). 4. Wide viewing angle: The unit offers a wide viewing angle of 100 degrees, both vertically and horizontally 5. Vivid-color display without double images: The pixel electrode also serves as a reflector to eliminate double reflections. ECB-Method Reflective STN Color LCDs
High-definition clear color images without a backlight and color filter This Reflective STN Color LCD is based on a newly developed electrically controlled birefringence (ECB*) technology that delivers a high-brightness, high- definition display with low power consumption while eliminating the need for a backlight and color filter. It is capable of delivering a true black display more sharply defined than previously possible, and this new color LCD display achieves crisp, clear reproduction of both text and images. 1. A single pixel allows a continuous color display of white, black, blue, green and red. The unit offers a true black display that makes it possible to deliver crisp and clear presentations of both text and images. 2. Bright background colors: Sharp's new phase differential plate, a new liquid crystal material system, as well as reflector with high reflectivity, make it possible to attain bright, vivid background colors. 3. Low power consumption: Like the standard-type STN LCD unit, the ECB-method STN color LCD unit eliminates the need for a backlight and thus reduces the power consumption level. * Electrically Controlled Birefringence (ECB) Changing the voltage applied to the liquid crystal layer modifies the tilt of the liquid crystal molecules. The resulting change in birefringence of the liquid crystal layer is detected by the two polarizers. This system is used for color displays. Making display and pen-based input technologies available by combining LCD input and detection panels Low cost, lightweight, high-definition LCDs with low power consumption are in great demanded for use with pen-input panels, and there are more than three methods currently in practical use for designing such applications. These include a pressure-sensitive method (used in Personal Information Tool and others), an electrostatic induction method and an electromagnetic induction method. The most conventional system coordinates detecting sensor plates that are piled on top of an LCD panel's structure, thus allowing pen-based input. The combination of LCD input and detection plates in one body have eliminated the need for other sensory tablets, and offer the
ability to streamline recognition functions. This pen-based input is now widely used in PCs, word processors, and various other products.
Sharp LCD Office Information Management System nicknamed "Prostation"-LW Series (for Japanese market) Meeting all the needs of modern office communications Prostation is a new pen-operated computer equipped with a large 10.4-inch color LCD display that allows easy and quick operation with just one touch of a stylus or fingertip. Simply use Prostation, and group communications become incredibly convenient with a "Screen-Shared Interactive Dialog Function." With this feature, users can communicate with another by writing a message on the pad with a stylus, simultaneously transmitting the contents to the receiving user's Prostation. A "Voice-Assisted Handwritten Memo Function" enables users to communicate through both written and voice-assisted means. "Electronic Mail Software" allows users to efficiently transmit information via digitally handwritten memos. .Giant Microelectronics
Enlarged view of TFT LCD Expanding LCD horizons with "giant microelectronics" In addition to utilizing "microelectronics" technology to create high picture quality LCDs, R&D is being focused on "giant microelectronics" technology which makes it possible to successfully create large screen LCDs with incredibly high picture quality. Sharp is currently working on developing: Advanced miniaturization technology Highly reliable production technology Development of new production structures Pursuing high picture quality through advanced micro-technology There are two essential technologies required to develop LCD high picture quality: Increase the number of pixel
Make conductors and thin-film transistors (TFTs) as small and as narrow as possible to increase the pixel surface area The Ever-Expanding LCD Market
Changes in Semiconductor/LCD Market Output Like semiconductors, the LCD market is expected to grow rapidly Based on the interrelationship between the semiconductor and LCD markets, it is clear that the LCD market is currently 15 years behind the semiconductor market in terms of growth. It is estimated that, like semiconductors, which experienced tremendous market growth during the 1980s, the LCD market will begin to expand rapidly in the late 1990s and grow to be worth 2 trillion yen by the year 2000. LCD panel Dimension Technologies 2015XLS 15 se od ostatních panelů odlišuje možností vytvořit „opravdový“ 3D efekt. Jak to funguje? Jde o podobný princip, jako v případě tzv. 3D brýlí (ke svým grafickým kartám je „bundluje“ například Asus nebo Elsa), což znamená, že scéna se rozloží pro levé a pravé oko zvlášť. Ovladač grafické karty ze Z-bufferu přečte informaci a hloubce bodu a nechá zpracovat jeden snímek pro levé oko a druhý jakoby perspektivně posune pro pravé oko. Technologie použitá v tomto LCD panelu je ale jedinečná tím, že promítaný bod je natočený příslušným směrem (k levému a pravému oku). K správné funkci tudíž potřebujte pouze ovladač k monitoru a z 3D zobrazení se mohou těšit i uživatelé koukající se na monitor z jiného úhlu. Při zobrazení tak máte dojem, že „hloubka“ je uvnitř monitoru. Redaktory serveru Tech Zone, kde se tímto LCD panelem zabývali podrobněji, zvláště překvapila dobrá ostrost a podsvětlení. Nevýhodou tohohle bezpochyby zajímavého kousku hardwaru zůstává cena, která se pohybuje okolo 1700 dolarů, což je částka akceptovatelná opravdu jen pro hrstku počítačových nadšenců Virtuální realita Přestože se ve smyslu těchto slov dá za virtuální (neskutečnou) realitu označit kdejaké počítačem realizované prostředí, je v poslední době tento název používán především jako označení nového a velice perspektivního oboru, který se zabývá využitím různých moderních technických zařízení pro realizaci zcela převratného způsobu komunikace s počítačem. Jedná se o úplně nové uživatelské rozhraní, jehož cílem je pokud možno co nejvíce přiblížit počítačové prostředí
skutečnosti tak, jak ji zachycují naše smysly. Uživatel by měl být do tohoto prostředí co nejvíce vtažen (ponořen). Současné aplikace virtuální reality pracují se zrakem, sluchem a hmatem. Experimentuje se i s čichem a chutí. Nástroje (zařízení, pomůcky), které ve spojení s co nejrychlejším počítačem na úrovni pracovní stanice takovéto aplikace realizují, jsou základem úspěchu. Můžeme je rozdělit podle smyslů, na které působí. Zraku je třeba předložit kvalitní trojrozměrný prostorový obraz. Aby byl reálný, to znamená pohyblivý, musí být zařízení schopno zobrazovat jednotlivé obrazovky tak rychle za sebou, že uživateli splývají v plynulý pohyb. Čím je tato frekvence vyšší (viz monitory), tím je obraz kvalitnější. Hranice, při které je lidské oko schopno zaregistrovat jednotlivé obrázky, leží okolo 20 obr./s, skutečně přirozený dojem vzniká až při použití frekvence okolo 50 obr./s. Má-li být obraz navíc prostorový, musí být pro každé oko poněkud odlišný (stereoskopický). Často se pro tyto účely používají speciální brýle, které pomocí filtrů zajistí, aby každé oko vidělo pouze to, co má. Tento způsob zobrazení (kina, televize, monitor počítače) má však dost daleko k dokonalosti. Zobrazovacím zařízením ve virtuální realitě běžně používaným jsou spíše různé stereoskopické displeje nejčastěji zabudované do přilby, aby byly v blízkosti očí. Pro každé oko je zde jeden LCD (tekuté krystaly) panel nebo miniaturní obrazovka. Speciální optika zajišťuje co nejširší zorné pole (horizontální rozsah vidění bez pohybu hlavy a očí). Dosahuje se okolo 120 ° ze 180 ° ve skutečnosti. Aby byl dojem reality pokud možno co nejdokonalejší, je třeba zajistit, aby se obraz příslušně měnil podle pohybu očí i celé hlavy. Zvláštní zařízení v přilbě zabudované předává počítači informaci o poloze hlavy a očí. Dojde-li ke změně, musí počítač v reálném čase nový obraz vygenerovat a zobrazit ho na displeji. Přestože se používají na urychlení těchto operací různé triky (detaily pouze ve středu obrazu, prostředí vektorově popsané modelem a generované počítačem), ani ty nejlepší současné počítače nejsou schopny dostatečně rychle reagovat na prudké pohyby hlavy a očí. Zvuk se ve virtuální realitě řeší podobně jako obraz. Do přilby jsou zabudována sluchátka jako nezávislý zdroj zvuku pro každé ucho. Vystačit s klasickým statickým stereofonním zvukem však lze jen u těch nejprimitivnějších aplikací. Požadavkem dneška je dokonalý prostorový interaktivní zvuk. Prakticky to znamená, že počítač musí pracovat s co nejdokonalejším akustickým modelem daného prostředí včetně různých detailů. Pak je schopen vygenerovat výsledný zvuk v kterémkoli místě jako součet všech zdrojů, které v daném prostoru existují, navíc v závislosti na momentálním otočení hlavy uživatele. Nebudu zacházet do větších detailů, jen je třeba si uvědomit, že jedině takovýto způsob realizace zvuku dovoluje dostatečné přiblížení k realitě. Slyšíte-li nějaký zvuk za sebou, můžete se otočit a bude před vámi. Budete-li chtít, můžete se k němu i přibližovat a vzdalovat se. Posledním ze smyslů, na něž dokáží současné prakticky používané aplikace virtuální reality působit, je hmat. Vytvořit dojem, že prostředí, které vidíte i slyšíte, také cítíte, je velice obtížné a zdá se, že ještě dlouho zůstane nejslabším místem těchto aplikací. Zařízení, které se k těmto účelům používá, se nazývá datový oblek. Kvalitní datový oblek splňuje dvě základní funkce. Jednak informuje počítač o pohybu uživatele ve virtuálním prostoru a zároveň poskytuje uživateli zpětnou vazbu ve formě hmatové i silové informace o vlastnostech prostoru. Předmět, který zvednete, musíte nejen cítit v prstech, ale musíte mít též pocit, že něco váží. Skutečně realistické řešení tohoto problému včetně rozpoznávání změny teploty, přenosu silového působení z určitého místa na celé tělo nebo bolestivé reakce v případě prudkého nárazu, to vše současná technika dosud řešit nedovoluje. Datový oblek je velice drahý a mít ho na těle i s přilbou je dost nepříjemné. Proto se často používá pouze datová rukavice, v jednodušších případech dokonce bez zpětné vazby. Rozlišujeme tři základní stupně virtuální reality. Pasívní aplikace fungují podobně jako film. Takové prostředí můžete vidět, můžete ho slyšet a určitým způsobem třeba i cítit, ale nemůžete ho žádným způsobem ovlivňovat. Režie tj. řízení průchodu je plně v rukou programu. Typickým příkladem takové aplikace může být třeba představení stereoskopického filmu (s brýlemi) s mnohokanálovým zvukem a navíc ve specializovaném panoramatickém kině, kde se celé hlediště pro umocnění dojmu pohybuje. Ještě silnějším zážitkem mohou být některé atrakce v zábavních parcích. Jedná se o moderně vyhlížející kabinu o velikosti malého autobusu. Do té si sednete,
připoutáte se a můžete si třeba virtuálně sjet Niagarské vodopády nebo zažít něco jiného podobně vzrušujícího. Do této kategorie by bylo možno zařadit snad také telekonference. Několik lidí, každý ve skutečnosti na jiném konci světa, sedí spolu v jedné místnosti. Přitom se navzájem vidí i slyší, takže jim nic nebrání řešit důležité problémy. Nemohou se ale neomezeně pohybovat, ani si podat ruce. Druhým stupněm jsou aplikace aktivní. Zařízení v tomto případě dovoluje virtuální prostředí libovolně zkoumat. Je možno se v něm pohybovat, prohlížet si ho ze všech stran i slyšet odpovídající zvuk. Většinou zde však chybí hmatová zpětná vazba, a tak není možno toto prostředí žádným způsobem modifikovat. Nelze virtuálně přemisťovat předměty, otvírat dveře apod. Uživatel se pohybuje podobně jako duch. Může procházet stěnami i prostrčit ruku libovolným předmětem. I tak může být taková procházka nevšedním zážitkem. Prakticky se tento stupeň používá například k vyvolání dojmu, který může mít určitý léčebný efekt u pacientů postižených různými fobiemi (třeba strach z výšek) nebo duševními poruchami. Jinde může sloužit k prezentaci virtuálních uměleckých děl, k prohlížení dosud nepostavených budov, pro vizualizaci informací v bankovnictví, v meteorologii, v řízení letového provozu a v různých vědních oborech (trojrozměrné zobrazení funkcí více než dvou proměnných) nebo k hledání nepřítele v neznámém prostředí za účelem jeho likvidace. Zbraně u takových atrakcí použité jsou částečně skutečné (tvar a spoušť) a částečně virtuální (střela). Podobné mnohem dokonalejší systémy, kde se zčásti používá ovládání podobné skutečnosti ve spojení s virtuálním obrazem a zvukem, používají vojáci k simulaci střelby, v leteckých trenažérech nebo k ovládání robotů na dálku (zamořený prostor, hašení požáru). Nejdokonalejšími a také technicky nejnáročnějšími jsou aplikace plně virtuálně interaktivní. Ty dovolují prostředí nejen zkoumat, ale také ho modifikovat. Je možno brát virtuální předměty do ruky a přemisťovat je, pracovat s virtuálními nástroji, mačkat různá virtuální tlačítka, psát na virtuální klávesnici apod. Za vrcholnou aplikaci v této kategorii lze považovat třeba virtuální cvičnou operaci, kterou může chirurg opakovaně uskutečnit na modelu určitého orgánu konkrétního pacienta dříve, než se do ní pustí ve skutečnosti. Nebo si zkuste představit architekta, který má možnost si svůj výtvor nejen prohlížet, ale též ho interaktivně měnit. Vezme stěnu a posune ji, přemístí dveře nebo okna. Totéž platí o nábytku. Přitom může výsledek okamžitě sledovat ze všech stran. Technika virtuální reality se rychle zdokonaluje. Brzy bude možno ve virtuálním prostoru potkat virtuálního člověka, prohlížet si ho ze všech stran, mluvit s ním a třeba ho vzít i za ruku. Ten člověk přitom nemusí být zas tak úplně virtuální. Může to být model dokonale simulující skutečnou osobu, která se fyzicky vyskytuje někde hodně daleko, momentálně se též pohybuje virtuálním prostorem a všechny její pohyby včetně mimiky obličeje a hlasu jsou digitalizovány a pomocí sítě přenášeny do vzdáleného počítače, který tato data zobrazuje. Stačí, aby virtuální prostor, kde se obě postavy pohybují byl stejný a mohou se setkat skoro jako ve skutečnosti. Zní to možná dost fantasticky, ale takové experimenty se již provádějí. Cena potřebných zařízení je dosud tak obrovská, že jsem sám zvědav, kdo si bude moci dovolit tyto možnosti prakticky využít. Mohou to být třeba virtuální porady vedení nějaké bohaté banky nebo centrální celosvětová burza cenných papírů nebo setkání hlav světových mocností. Nevím, jak se těchto možností zmocní zábavní průmysl, doufám však, že tak daleko, aby bylo možno někomu virtuálními pomůckami skutečně ublížit, nikdy nedojdeme. Hodně se též mluví o virtuálním sexu. To bude panečku senzace, až bude dívka měsíce na serveru Playboje třírozměrná a hmatatelná. Ke skutečnosti to však bude mít jistě ještě hodně daleko. Nevím, jestli vás to uklidní, ale již dnes začíná být zřejmé, že se hned tak nepodaří přiblížit virtuální realitu skutečnosti podobně, jako se dosud nepodařilo vytvořit umělou inteligenci, která by se mohla srovnávat s lidskou. S tvůrcem přírody soutěžit nelze. Jednou věcí jsem si docela jist. Ve školství se s virtuální realitou ještě hodně dlouho nesetkáme. Zamysleme se přesto alespoň teoreticky nad tím, jak by se zde dala využít. Virtuální realita se jednou nepochybně stane docela přirozeným uživatelským rozhraním konstruktivních výukových aplikací. Není problém si s trochou fantazie představit, jak děti v programu Explores the Human Body, který byl v kapitole pojednávající o výukových programech popisován, zkoumají lidské tělo zevnitř trojrozměrně a s využitím hmatu. Nebo jak cestují po planetách sluneční soustavy a zkoumají je zblízka. Nesrovnatelně názornější bude ve virtuálním prostoru modelování a experimentování. Zkuste si třeba představit model počítače, který bude možno za chodu zkoumat zevnitř s možností názorného zobrazení funkce jednotlivých dílů. Fantastické možnosti jednou přinese virtuální fyzikální laboratoř. Zde bude možno nejen modelovat, ale též pomocí experimentů ověřovat různé jevy. Možnost prostorového zobrazení zjištěných závislostí spolu s interaktivní
změnou parametrů dovolí mnohem snadnější pochopení principů a může přispět třeba i k objevu zcela nových netušených souvislostí. Virtuální realita se uplatní i ve zpřístupnění informací dostupných prostřednictvím vzdálených sítí. Taková síť bude (podobně jako v programu Creative Writer) ulicí, kde budou jednotlivé domy představovat datové servery nebo různé služby, kam bude možno vejít podobně jako do knihovny, na poštu, do trafiky pro noviny nebo do jiného obchodu, na návštěvu k firmě, jejíž výrobky nás zajímají apod. Zkuste si na závěr představit třeba virtuální návštěvu archeologického muzea. Zde bude nejen možno si prohlížet a třeba vzít i do ruky různé vzácné archeologické nálezy, ale též zblízka zkoumat současný stav vykopávek na různých místech světa a třeba i rekonstrukci významných památek v různých obdobích a to včetně tehdejšího způsobu života. Doufám, že si každý umí představit, jak by mohlo vypadat třeba geografické muzeum nebo jakékoli jiné a jak by se dalo využít ve výuce. Byl bych neobyčejně šťasten, kdyby naše děti měly šanci podobné vymoženosti co nejdříve využívat. Cesta k tomu však bude ještě dlouhá a trnitá. Je však mnoho věcí, které pro zlepšení zapojení informačních technologií do výuky můžeme udělat již teď.
Závěr LC displeje se vyskytují ve velkém množství aplikací. Obecně, jejich výhodou je malý odběr zobrazovací matice (řádově desítky mikroampérů), malé rozměry a nízká hmotnost ve srovnání s klasickou elektronovou obrazovkou, lepší geometrie a ostrost zobrazení, delší životnost, stálost obrazu (LC displeje mají mnohem vyšší kmitočet obnovení informace a jejich fyzikální princip umožňuje mnohem delší "dosvit", takže odpadá klasické blikání, nešvar to elektronových obrazovek a displejů)... Nevýhodou, která je však již u některých displejů odstraněna (na úkor ceny), je teplotní závislost, kdy kapalné krystaly při záporných a vysokých kladných teplotách ztrácejí své fyzikální vlastnosti a displej přestává dočasně pracovat.
Odkazy na internetové adresy: ¨ www.howstufforks.com//lcd.htm - použití LCD, historie tekutých krystalů, sestavení jednoduchého LCD, princip na kterém LCD pracuje, světelný zdroj pro LCD – studená katodová fluorescenční lampa, pasivní a aktivní matrix, barevné pixely a budoucnost http://www.sharp.co.jp/sc/library/lcd_e/s2_1_1e.htm - příklady použití LCD, co jsou ¨ kapalné krystaly, historie, - princip LCD technologie,schémata ¨ www.webopedia.com/term/LCD.html - stručně o LC ¨ http://hw.cz/docs/lcd_iq_displaye/lcd_iq_dip.html - výhody a nevýhody LCD ¨ http://www.hamoun.cz/sh/Sh.nsf/v/4364100287AF1375C1256AC5003A9369 - 3D technologie ¨ http://omicron.felk.cvut.cz/%7Ebobr/ucspoc/virtreal.htm - virtuální realita ¨ http://www2.itt.cz/index.php - komerční údaje o LCD monitorech ¨ http://www.vartechdisplays.com/products/topics/lcd.asp - LCD technologie - stručně
