Flat-Panel Displays
Flat-panel displays (FPDs) are thin, bright display outputs that are gaining a foothold on desktop computer systems as a replacement for traditional CRT monitors. They require a much smaller desk space because they do not have large cases that house electron guns, nor a heavy glass front. They do not rely on transitory phosphors to create an image and are therefore free from flicker. FPDs have flat screens and there is thus no distorted image at the edge of the viewing area, as there is with curved CRT monitors. They however, have limited optimal viewing angles Most FPDs also lack the range of resolutions of the CRT-based monitors and require a digital graphics adapter card that is tuned to that FPD.
Several different types of FPDs are available today, varying in cost, image quality, and several other factors that affect both suitability to different computing applications and user acceptance.
Liquid Crystal Displays (LCDs) form an image by using transparent organic polymers sandwiched between a pair of polarizing filters, with some form of back-lighting. The filters are set at a 90-degree angle to each other. In an uncharged state (no current applied), the crystals are aligned so that light can pass through the top filter. When a current is added, the crystals align to the electric field, blocking the transmission of light. Color light-emitting diode (LED) displays have three adjoining cells, each equipped with a different RGB color filter.
Electroluminescent Displays (ELDs) actually emit light, rather than simply controlling the transmission of a back-light source. The light generation comes from phosphors layered between front and back electrodes. Most ELD products are found in technical applications as well as ATM machines.
Plasma Display Panels (PDPs) work much like the fluorescent lights by energizing an inert gas. Phosphor films are used to produce a color image. This technology is used to manufacture very large FPDs. Like fluorescent lights, PDPs are relatively inexpensive to produce, but lower contrast and brightness, as well as higher relative power consumption, have limited their use for computer applications.