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Modern aircraft are incredibly complex machines. Although many, if not most, of the functions are automated, the pilot and other cockpit crew members must have access to large amounts ofinformation in a very small period oftime. And this information must be available to them in a format that is easily understood quickly. Today, this information is often provided by Cathode Ray Tube (CRT) screens. These CRTs have many advantages with respect to visualization. That is, color CRTs can have full color, high brightness, large viewing angle, high contrast, and high spatial resolution. The disadvantages lie, to a great extent, in the package. CRTs and their necessary electronics are large, heavy, and fragile. Furthermore, ifbroken accidentally, the resulting implosion can create disaster in the cockpit. Consequently, many display developers of cockpit displays believe that the ideal display should be full color, extremely thin, light weight, energy efficient, exhibit high brightness and high dynamic range, capable of being refreshed in real time without jitter, have high spatial resolution, display a large number of pixels, and be visible over a very wide range of angles (normal to grazing incidence both left-to-right and top-to-bottom). For military aircraft, the display should operate with the same characteristics over a very wide temperature range. This is particularly important in northern climates during the winter, or when the interior ofthe aircraft becomes very cold such as a result of damage to the aircraft body at high altitude (e.g. gunfire, missile attack). In cockpits, the display should also be available in a wide range of sizes include the possible use in head or helmet mounted configurations. There has also been the suggestion that virtual reality glasses might be beneficial in aircraft cockpits. The displays would be available not only for normal instrument readings but also for radar, mapping, computer monitors, and possible cockpit lighting. The ideal cockpit display should exhibit the same full color visual characteristics whether seen in direct sunlight during the day or in a darkened cockpit at night. Some cockpit applications are looking forward to wraparound displays. Todays best information-comprehensive displays for cockpit use are fast-refresh, high brightness cathode ray tubes (CRTs). Unfortunately, a single CRT takes up a lot of room since the depth ofthe CRT is often greater than the screen diagonal. The CRT's fragility impacts cockpit safety. Its brightness is limited by a scanning electron beam which comes from a low current density thermionic cathode. Its lifetime is often a problem because ofbarium evaporation from that same cathode. The CRT cathode needs its own power supply and a separate magnetic scanning circuitry. In fact, most of its energy is wasted on the cathode and scanning circuitry. The energy is not delivered to the user as useful, visible light. Nevertheless, the CRT is still the best display available for cockpit display applications because it creates its own full-color light by cathodoluminescence. Some flat-panel technologies are becoming feasible for cockpit applications, but the CRT is still projected to have a favorable cost-benefit ratio, and superior performance characteristics for some years to come.
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