Flat Panel Displays Information
Flat panel displays (FPDs) are thin, flat electronic devices used to display:
- alphanumeric data
There are several basic types of products. Digital light processing (DLP) displays are arrays of small mirrors on a semiconductor. Each mirror is a pixel, and the mirrors move quickly to produce an image. Electroluminescent displays (ELDs) or EL displays sandwich a thin phosphorescent film between two plates. One plate is coated with vertical wires. The other is coated with horizontal wires. Together, the plates form a grid. Liquid crystal displays (LCDs) sandwich a liquid-crystal solution between two sheets of polarizing material. Passing an electric current through the liquid causes the crystals to align so that light cannot pass through them. Light-emitting diode (LED) displays are used in high-resolution products. Organic LEDs (OLEDs) are a special type of FPD that uses organic compounds in the emissive layer. In a plasma display, a gas fills the spaces between two glass sheets that are lined up in parallel and separated by a gap just 100 to 200 microns wide. Ultraviolet (UV) light is generated by discharging the gas and using electrodes. Surface conduction electron emitters (SEDs) are FPDs that use an electron emitter to excite a phosphor layer for each pixel. SEDs offer many of the advantages of traditional cathode ray tubes (CRTs), but in a flat-screen format.
FPDs differ in terms of display technology. Cholesteric liquid crystals (ChLCDs) use the pitch of the liquid crystals to reflect light of desired wavelengths. There are two LCD matrix types: active matrix LCDs (AMLCDs) and passive matrix LCDs (PMLCDs). Color super-twist nematic (CSTN) displays are similar to LCDs and found in portable, laptop, and handheld devices. Double layer super-twist nematic (DSTN) displays are also available. High-performance addressing (HPA) is a passive-matrix technology that offers better response times and contrast than CSTN. Both multi-domain vertical alignment (MVA) displays and patterned vertical alignment (PVA) displays have fast response times, wide viewing angles, and a high contrast ratio; however, they suffer from diminished brightness and color reproduction. Super in-plane switching (S-IPS) provides better viewing angles than other display technologies, but is used mainly in large panels. Thin-film transistor (TFT) displays are active-matrix FPDs that produce color images which are as sharp as traditional CRT displays. Twisted nematic (TN) displays are relatively inexpensive, but have small viewing angles and provide poor color.
Selecting FPDs requires an understanding of FPD video standards. Quarter-video graphics array (QVGA) is a small display used in mobile devices. Video graphics array (VGA) supports text at a minimum resolution of 80 x 25 characters in 16 colors. Graphics are supported at a maximum resolution of 320 x 200 pixels in 256 colors, or 640 x 480 pixels in 16 colors. Super video graphics array (SVGA) displays provide greater resolution than VGA displays. All SVGA products support a palette of 16 million colors, but the number of colors that can be displayed simultaneously is limited by the amount of video memory installed. Extended graphics array (XGA) is a high-resolution graphics standard that is designed to replace the older 8514/A video standard. Super extended graphics array (SXGA) provides a higher resolution (1280 x 1024) than XGA (1024 x 768). Widescreen extended graphics array (WXGA), the widescreen format of XGA, is popular in television displays and has a resolution of 1280 x 800 pixels. Video standards for FPDs also include:
- SXGA+ (1400 x 1050)
- WSXGA+ (1680 x 1050)
- UXGA (1600 x 1200)
- WUXGA (1920 x 1200)
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