LCD
    n 1: a digital display that uses liquid crystal cells that
         change reflectivity in an applied electric field; used for
         portable computer displays and watches etc. [syn: liquid
         crystal display, LCD]

	

	LCD
       Liquid-Crystal Display (LCD)

	

	LCD
       LISP Code Directory (EMACS)

	

	LCD
       Loss of Cell Delineation (UNI, ATM)

	

	liquid crystal display
LCD

    (LCD) An electro-optical device used to display
   digits, characters or images, commonly used in digital
   watches, calculators, and portable computers.

   The heart of the liquid crystal display is a piece of liquid
   crystal material placed between a pair of transparent
   electrodes.  The liquid crystal changes the phase of the
   light passing through it and this phase change can be
   controlled by the voltage applied between the electrodes.
   If such a unit is placed between a pair of plane polariser
   plates then light can pass through it only if the correct
   voltage is applied.  Liquid crystal displays are formed by
   integrating a number of such cells, or more usually, by using
   a single liquid crystal plate and a pattern of electrodes.

   The simplest kind of liquid crystal displays, those used in
   digital watches and calculators, contain a common electrode
   plane covering one side and a pattern of electrodes on the
   other.  These electrodes can be individually controlled to
   produce the appropriate display.  Computer displays, however,
   require far too many pixels (typically between 50,000 and
   several millions) to make this scheme, in particular its
   wiring, feasible.  The electrodes are therefore replaced by a
   number of row electrodes on one side and column electrodes on
   the other.  By applying voltage to one row and several columns
   the pixels at the intersections are set.

   The pixels being set one row after the other, in passive
   matrix displays the number of rows is limited by the ratio of
   the setting and fading times.  In the setup described above
   (known as "twisted nematic") the number of rows is limited
   to about 20.  Using an alternative "supertwisted nematic"
   setup VGA quality displays (480 rows) can be easily built.
   As of 1995 most notebook computers used this technique.

   Fading can be slowed by putting an active element, such as a
   transistor, on the top of each pixel.  This "remembers" the
   setting of that pixel.  These active matrix displays are of
   much better quality (as good as CRTs) but are much more
   expensive than the passive matrix displays.

   LCDs are slimmer, lighter and consume less power than the
   previous dominant display type, the cathode ray tube, hence
   their importance for portable computers.

   (1995-12-09)