The Global Impact of Digital Display Technology (from April 1997)
Throughout history, humans have created various methods of displaying information. We have invented drawing and writing to store information and to carry information to others. Because technology is now a major part of our culture, the need to carry information between people and machines has become very important. Of the human senses, the greatest amount of information can be transmitted to the brain by the eyes.
The eye can adapt to varying amounts of darkness, movement, and depth. Each eye has the ability to focus light on 125 million rods and cones, or light receptors. The enormous amount of light and color information captured by the eye is carried in parallel to the brain via the optic nerve. This high-bandwidth pathway makes human vision ideal for communications from machines to humans. Therefore, electronic displays take advantage of the most effective of the human senses.
Due to the large amount of computer information now available, the need to display dynamic, changing information has become important. Another development has been graphic information displays. In some cases, people can see and react faster to pictures, lights, or colors than the equivalent information expressed in words. This trend is especially evident in computer software, which now uses various icons and graphic metaphors to represent commands or complex information.
Another reason for using graphics instead of text is to increase the globalization of software packages. It is more profitable to create software packages that use graphics and can be used by people who speak any language, rather than creating language-dependent text-based software which cannot be sold worldwide. One major effect of this is that American software companies have created a cultural imperialism of information technologies, similar to the cultural imperialism of some types of mass media.
The first major step in early display technology was the incandescent electric light bulb. Light bulbs are filled with an inert gas and contain a wire, usually made of tungsten. When electric current runs through the wire, heat is produced which causes the wire to glow. The light is radiated through the bulb and is then used by people for many purposes. One main purpose is illumination indoors or at night. However, the need to display information made the incandescent light useful for some electronic displays.
Lights used in such displays are used to convey information about our surroundings or information sent from other people. Some common examples include traffic lights, as well as automotive dashboard and signal lights. This type of information display is good for displaying simple information that needs to be seen from a distance. However, such displays are very limited in that they display only on/off or yes/no types of information. Often, various colors of light are used to display different types of information. Also, arrays of incandescent lights can be useful for displaying more complex information, such as time of day, temperature, or short advertisements on electronic billboards. But such displays take up a lot of space, are expensive to manufacture, and consume a large amount of power. They also do not display a large amount of information.
It was not until the development of the cathode ray tube (CRT) that high-quality electronic text and graphic displays became feasible. The CRT works by emitting electrons at a phosphorescent screen. The CRT is used in oscilloscopes, computer monitors, and is also a major component of television. By directing the stream of electrons, scan lines can be created on the screen, which can create detailed two-dimensional images, including pictures and text.
The development of the CRT enabled the manufacturers to make computers that could display a large amount of information to users. Although CRT displays provide good picture quality and are inexpensive, the CRT is not very portable, and uses a significant amount of power. This type of display is very suitable for desktop computers, and was the only popular computer display technology until the development of laptop computers.
Desktop computers have transformed the workplace from paper to electronics. Information is now stored and accessed far more quickly and reliably than the filing cabinets that paper offices use. Ironically, because electronic information can be printed easily, the actual amount of paper used has increased. These paper documents are not used to store the information, but are just reports that are sometimes looked at before being thrown in the trash. This technique is used to escape the limitations of computer monitors, which cannot be carried around, paged through, and discarded. Therefore, the computer printer has become a slow and costly variation of the computer monitor. The paper-less office will not become a possibility until electronic displays are as portable as paper and show just as much clarity and information capacity.
Of all the uses of the CRT, the impact of television on society is the most obvious. Broadcast media have, to some extent, replaced books as well as interactive communications with other people. To a small degree, interactive computer technology may reverse that trend by making information and other people more accessible. But the CRT still lacks the ability to make truly portable information displays available.
With the development of semiconductors, the light emitting diode (LED) has emerged which provided miniature lights which were much more energy efficient than incandescent light bulbs. This allowed consumer electronics companies to start using small displays in all kinds of devices. LED's are very small and easily arranged into segments to allow numbers or letters to be displayed. Devices using such displays include VCR's, some early calculators, and digital watches. The LED was a major step toward portable displays, but it still consumed enough power to drain batteries rapidly and did not offer the full-screen text and graphics displays that the CRT offered. The LED is mainly used to replace incandescent lights for on/off indicators, and is also useful for devices in low-light conditions such as digital alarm clocks.
The next step in display technology was the liquid crystal display. We are familiar with the solid, liquid, and gas phases of matter. But scientists in the late nineteenth and early twentieth centuries, experimenting with complex molecules, discovered another phase of matter between the liquid and solid phases. In 1888, Friedrich Reinitzer, an Austrian botanist, discovered molecules based on cholesterol that have such a phase. This phase, called the liquid crystal phase, has properties of both liquids and solids. Molecules in the liquid crystal phase can move around, just as in the liquid phase. But they tend to be oriented in the same direction, like molecules in the solid phase.
Research of liquid crystals was relatively slow until 1968, when two scientists at RCA showed that liquid crystals, in thin layers, changed their optical characteristics when electrical voltage was applied. By directing the light though polarizing filters, the reflectivity or darkness of the display could be varied. Over the next ten years, great advances in liquid crystals were made, producing good display quality and using very low power consumption. Such characteristics made their use ideal for battery-powered watches and calculators. Today, liquid crystals are also used in telephones, cameras, thermometers, pocket-size TV's, projection TV's, and many other devices.
Unlike other displays, such as the CRT, LED, or the incandescent light, LCD's cannot produce their own light. They rely on ambient light or supplemental light from another source to reflect off the surface of the LCD. This tends to make them hard to see in low-light conditions. Manufacturers have solved this problem by integrating lighting into some displays, called backlighting. This feature allows watches to be used at night and makes laptop computers far more flexible.
By creating an array of millions of dots, much like a newspaper photograph, color high-resolution LCD's have been manufactured for laptop computers. These displays, known as flat panel displays, allow portable computers to be used without the bulky CRT monitors used in desktop computers. Also, new flat panel displays are using gas plasma or electroluminescent display technologies. Because of the power consumption and manufacturing cost, the LCD remains the dominant flat panel display technology.
Because flat panel displays can have over a million dots of color, the electrical lines running to the display are multiplexed to reduce the complexity of the hardware. The picture quality usually degrades due to this multiplexing process. To correct this problem, some flat panel displays are manufactured with an integrated thin film of transistors on the surface of the liquid crystal display to compensate for the multiplexing noise. With electronics built into the display, these smart displays, called active matrix displays, are becoming very popular in laptop computers. Earlier flat panel displays, which have only external electronics and do not correct for multiplexing, are known as passive matrix displays. These simpler displays tend to have a blurring effect and relatively low contrast, but are much cheaper to manufacture. Both types of display are still commonly used as output devices.
Although display technologies are normally used for output devices, designed to convey information to a person, some companies have merged touch sensors with electronic displays. The new touch screen displays offer the ability to simply touch the screen to select icons, or to "write" on the screen with a stylus. A computer can use this form of input instead of a keyboard or mouse. The touch screen displays are now common at department stores, offering easy-to-use computer access to product information.
The strongest effect of flat panel displays on society is evident with the development of the laptop computer. Modern laptop computers enable business travellers to take their computer with them on business trips, to meetings, and sometimes on vacations. College students can be free from working at a bulky desktop computer and can take their files anywhere. Portable information displays have greatly impacted the lives of many people. These displays are necessary for digital watches, calculators, pagers, and cellular phones. They have enabled laptop computers to give people more portability and productivity.
Some new advances are just now starting to work their way into society. Small hand-held, or palmtop, computers are now available. These pocket-size palmtop computers are using a touch-screen LCD to display graphics and text. They allow extreme portability with the power of a desktop computer. They also have the communications ability to allow a user to send e-mail or browse the web, even over a cellular phone. This next step in portability is likely to have great business and educational benefits.
In the opposite direction, efforts are also being made to increase the size of flat panel displays. By making the flat panel displays larger, they can exceed the picture quality of the CRT. A new flat wall-hanging television, called the Plasmatron, is under development at Sony. Compared to the CRT, a flat panel television takes up less space, can have a better picture, and does not suffer from the distortion of the curved surface of a CRT. It is also possible that large wall-hanging televisions may eventually be useful for just displaying pictures or artwork. This could, in some homes, replace the conventional paintings and other wall decorations with continually changing scenery, in addition to information displays.
Sometimes there is a need to display complex multi- dimensional information. Various graphing techniques have been developed to display this information on a flat display or a printed page. But some amount of confusion or loss of clarity can result. Other techniques using special glasses enable three- dimensional viewing on a two-dimensional display. Electronic displays are now being developed that allow virtual reality to show information in three dimensions. They work by integrating tiny LCD or CRT displays into head-mounted display devices. Virtual reality also uses motion sensors and 3D surround sound to produce a more realistic effect. Virtual reality technologies could revolutionize some communications media, especially in education, entertainment, and scientific research.
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