The document provides a comprehensive overview of liquid crystal displays (LCDs), detailing their functioning, applications, and advantages and disadvantages. LCDs are flat-panel displays used in devices like monitors and televisions, relying on a backlight and polarizing filters to display images through liquid crystals. The text also distinguishes between transmissive and reflective LCDs, highlighting their specific use cases and power consumption characteristics.

1. WELCOME
By
D . Sree Sravani,
15KT1A0423,
ECE-A.

2. Liquid Crystal Display

3.  A liquid-crystal display (LCD)
is a flat-panel display or
other electronic visual
display that uses the light-
modulating properties of liquid
crystals. Liquid crystals do
not emit light directly.

4. Applications
 LCDs are used in a wide range of
applications including computer
monitors, televisions, instrument
panels, aircraft cockpit displays, and
signage. They are common in consumer
devices such as DVD players, gaming
devices , clocks , watches ,
calculators, and telephones, and have
replaced cathode ray tube (CRT)
displays in nearly all applications.

6.  LCD (Liquid Crystal Display) panels are
“transmissive " displays, meaning they
aren't their own light source but instead
rely on a separate light source and then
let that light pass through the display
itself to your eye . We can start to
describe how an LCD panel works by
starting with that light source. The light
source is a very thin lamp called a "back
light" that sits directly behind the LCD
panel .

8. The light from the backlighting then
passes through a polarizing filter (a
filter that aligns the light waves in a
single direction). From there the now
polarized light then passes through
the actual LCD panel itself.
 The liquid crystal portion of the
panel either allows the polarized light
to pass through or blocks the light
from passing through depending on
how the liquid crystals are aligned at
the time the light tries to pass
through.

10. The liquid crystal portion or the panel is spit up
into tiny individual cells that are each controlled
by a tiny transistor to supply current. Three cells
side by side each represent one "pixel" (individual
picture element) of the image.
 Red, green and blue are the primary colors of
light. All other colors are made up of a
combination of the primary colors. An LCD panel
uses these three colors to produce color which is
why there are three cells per pixel — one cell
each for red, green, and blue.
Once the light is passed through the liquid crystal
layer and the final polarizing filter it then passes
through a color filter so that each cell will then
represent one of the three primary colors of light.

12. PROS & cons:
LCD displays are very thin. They can
be mounted in places traditional CRT
televisions and monitors cannot.
Color reproduction is excellent.
Contrast is good, although not great.
Pixel structure is very small, which
creates a very smooth image.
Durable technology.
No burn-in issues.

13. Very expensive technology per square
inch of viewing area.
Black levels and details in dark
scenes are not as strong as those in
competing technologies.
Dead pixels can be an issue, although
quality has improved as the
technology has matured.
Sizes above 40" are cost prohibitive.

14. Different types of LCD’s
Two common types of LCD are
1.Transmissive LCD
2. Reflective LCD

15. Transmissive LCD
The Transmissive LCD is illuminated
from one side and viewed from the
opposite side. Activated cells appear
dark and inactive cells appear bright.
One disadvantage of Transmissive LCD
is that lamp used to illuminate the
LCD consumes more power than
consumed by the LCD itself.

16. Reflective LCD
This is commonly used in pocket
calculators and digital watches. It is
viewed by ambient light reflected in a
mirror behind the display. They have
lower contrast than the Transmissive
type, because the ambient light
passes twice through the display
before reaching the viewer. The
advantage is that there is no lamp to
consume power, so the battery life is
long.

17. Advantages
• Does not rely on phosphors
• Easy disposal
• Energy efficient, low-power
• Excellent contrast
• Immune to screen image burn-in
• Lightweight and compact
• Low flicker rates
• Screens are available in a vast range of sizes
• Sharp resolution and imagery
• Superior resolution
• Used in battery-powered electronics
• Uses a smaller pixelated format

18. Disadvantages
• The color and contrast from various viewing
angles is inconsistent
• Features poor black on dark imagery
• Motion blur is common
• With brightness from backlighting, imagery
may appear flat
• Pixel-based display may be stuck on screen
• Fixed resolution
• Newer technology costs more
• Imagery not as good with analog interface