2.  A display device is a device for visual
presentation of images (including text)
aquired,stored, or transmitted in various
forms
Ex: computer monitor,TV screen etc.
 It is also called information display.

3.  Various technologies available are
 CRT cathode ray tube
 LCD liquid crystal display
 Plasma technology

4.  It is a type of flat panel display which is now
used commonly for large TV displays

5.  The xenon and neon gas in a plasma television
is contained in hundreds of thousands of tiny
cells positioned between two plates of glass.
 Long electrodes are also sandwiched between
the glass plates, in front of and behind the
cells
 Cells are covered with a magnesium oxide
protective layer.

9.  The display panel is only about 6 cm (2½
inches) thick, and total thickness less than
10cm
 Bright scenes will draw more power than
darker scenes
 Estimated life time is about 60000 hrs

10.  Over all thickness Is less than 10cm and can be
installed on wall
• Faster response time

11.  They are costly as compared to CRT,LCD
displays.
 Burn-in problem.
 Static images can leave a permanent mark
on the screen. This is why a plasma TV should
not be used as a computer monitor or video
game display

12.  Liquid Crystal Display
Definition
Principle
Classification

13.  A liquid crystal display is a thin, flat display
device made up of many number of pixels
arrayed in front of a light source or reflector. It
uses very small amounts of electric power.
 Generally used in calculators,laptops,etc.

14.  Each pixel of an LCD consists of a layer of
molecules aligned between two transparent
electrodes, and two polarizing filters,whose
axes are perpendicular.
 Orientation of the liquid crystal molecules is
determined by the alignment at the surfaces.

16. 1. Reflective twisted nematic liquid crystal display. filter film with a vertical axis to polarize light as
it enters.
2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes
that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.
3. Twisted nematic liquid crystal.
4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the
horizontal filter.
5. Polarizing filter film with a horizontal axis to block/pass light.
6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light
source.)

17.  Before applying Electric field, the molecules
arrange themselves in a helical structure, or
twist.
 When a voltage is applied across the
electrodes, a torque acts to align the liquid
crystal molecules parallel to the electric field ,
distorting the helical structure .
 This reduces the rotation of the polarization of
the incident light.

18.  Transmissive displays:
It is illuminated from the back by a backlight
and viewed from the opposite side (front).
Ex :Computer display.
• Reflective displays:
It is illuminated by external light reflected by a
diffusing reflector behind the display. Ex:
Calculator.