Mumbai University EXTC (Third Year) Sem 6 Television

1. Report on
Display Technology Comparison:
LCD / LED / PLASMA
Subject: Television
Teacher: Chintan Jethtva
T.E. Electronics & Telecommunication Semester VI
Submitted by
Kiran Chhatwani ( 09 )
Priyanka Holkar ( 22 )

2. INDEX
INDEX..............................................................................................................................................2
INTRODUCTION..............................................................................................................................4
BRIEF...............................................................................................................................................4
Liquid Crystal Displays:..................................................................................................................4
Liquid Crystal Displays With Light-Emitting Diode (LED) Backlighting: ...........................................4
Plasma Panels:...............................................................................................................................4
LIQUID CRYSTAL DISPLAY...........................................................................................................5
Definition:......................................................................................................................................6
History:..........................................................................................................................................6
Construction:.................................................................................................................................7
Working:........................................................................................................................................7
Advantages of an LCD’s: ................................................................................................................8
Disadvantages of an LCD’s:............................................................................................................8
Applications of Liquid Crystal Display:............................................................................................8
LED DISPLAY..................................................................................................................................9
Defination:...................................................................................................................................10
Working:......................................................................................................................................11
Full array..................................................................................................................................11
Edge lit.....................................................................................................................................12
Direct lit ...................................................................................................................................12
PLASMA DISPLAY ........................................................................................................................13
Definition:....................................................................................................................................13
Construction & Working:..............................................................................................................14
Step by step ..............................................................................................................................15
Advantages of Plasma Display:......................................................................................................15
Disadvantages of Plasma Display:.................................................................................................16
CONCLUSION................................................................................................................................17
Parameter....................................................................................................................................17
Contrast[does not distinguish "static" from "dynamic"] ................................................................17
Color depth...............................................................................................................................17

3. Response time...........................................................................................................................17
Frame rate.................................................................................................................................17
Environmental influences...........................................................................................................17
Flicker......................................................................................................................................17
Size ..........................................................................................................................................17
Energy consumption and heat generation ....................................................................................17
Maintenance .............................................................................................................................17
Electro-magnetic radiation emission ...........................................................................................17
Other........................................................................................................................................18

4. INTRODUCTION
Displays are electronic viewing technologies used to enable people to see content (still images, moving
images, text, or other visual material) in a range of entertainment, consumer electronics, personal
computer, and mobile devices, and many types of medical, transportation and industrial equipment.
In this report, we compare three Display Technologies, namely : LCD, LED and Plasma.
BRIEF
Liquid Crystal Displays:
Liquid crystal displays (LCDs) are lightweight, compact, portable, cheap, more reliable, and easier on the
eyes than cathode ray tube screens. LCD screens use a thin layer of liquid crystal, a liquid that exhibits
crystalline properties. It is sandwiched between two electrically conducting plates. The top plate has
transparent electrodes deposited on it, and the back plate is illuminated so that the viewer can see the
images on the screen. By applying controlled electrical signals across the plates, various segments of the
liquid crystal can be activated, causing changes in their light diffusing or polarizing properties. These
segments can either transmit or block light. An image is produced by passing light through selected
segments of the liquid crystalto the viewer. They are used in various electronics like watches,calculators,
and notebook computers.
Liquid Crystal Displays With Light-Emitting Diode(LED) Backlighting:
Some LCD screens are backlit with a number of light-emitting diodes (LEDs). LEDs are two-lead
semiconductor light source that resembles a basic "pn-junction" diode, except that an LED also emits
light. This form of LCD (liquid crystal display) is the most prevalent in the 2010s. The image is still
generated by the LCD.
Plasma Panels:
A plasma display consists of two glass plates separated by a thin gap filled with a gas such as neon. Each
of these plates has severalparallel electrodes running across it. The electrodes on the two plates are at
right angles to each other. A voltage applied between the two electrodes one on each plate causes a small
segment of gas at the two electrodes to glow. The glow of gas segments is maintained by a lower voltage
that is continuously applied to all electrodes. In the 2010s, plasma displays have been discontinued by
numerous manufacturers.

5. LIQUID CRYSTAL DISPLAY
A generic LCD TV, with speakers on either side of the screen
A Liquid-crystal-display televisions (LCD TV) are television sets that use liquid-crystal displays to
produce images. LCD televisions are thinner and lighter than cathode ray tube (CRTs) of similar display
size, and are available in much larger sizes. When manufacturing costs fell, this combination of features
made LCDs practical for television receivers.
An LCD is either made up of an active matrix display grid or a passive display grid. Most of the
Smartphone’s with LCD display technology uses active matrix display, but some of the older displays
still make use of the passive display grid designs. Most of the electronic devices mainly depend on liquid
crystal display technology for their display. The liquid has a unique advantage of having low power
consumption than the LED or cathode ray tube.
In 2007, LCD televisions surpassed sales of CRT-based televisions worldwide for the first time, and their
sales figures relative to other technologies are accelerating. LCD TVs are quickly displacing the only
major competitors in the large-screen market,the plasma display panel and rear-projection television.
LCDs are,by far, the most widely produced and sold television display type.

6. Definition:
Schlieren texture of liquid crystal nematic phase
four states of matter
Liquid crystals (LCs) are matter in a state which has properties between those of conventional liquids and
those of solid crystals.[1] For instance, a liquid crystalmay flow like a liquid, but its molecules may be
oriented in a crystal-like way.
History:
In 1888,[8] Friedrich Reinitzer (1858–1927) discovered the liquid crystalline nature of cholesterol
extracted from carrots (that is, two melting points and generation of colors) and published his findings at a
meeting of the Vienna Chemical Society on May 3, 1888 (F. Reinitzer: Beiträge zur Kenntniss des
Cholesterins, Monatshefte für Chemie (Wien) 9, 421–441 (1888)).[9] In 1904, Otto Lehmann published
his work "Flüssige Kristalle" (Liquid Crystals). In 1911, Charles Mauguin first experimented with liquid
crystals confined between plates in thin layers.
In 1922, Georges Friedel described the structure and properties of liquid crystals and classified them in 3
types (nematics, smectics and cholesterics). In 1927, Vsevolod Frederiksdevised the electrically switched
light valve, called the Fréedericksz transition, the essential effect of all LCD technology. In 1936, the
Marconi Wireless Telegraph company patented the first practical application of the technology, "The
Liquid Crystal Light Valve".

7. Construction:
LCD Layered Diagram
Simple facts that should be considered while making an LCD:
1. The basic structure of LCD should be controlled by changing the applied current.
2. We must use a polarized light.
3. Liquid crystal should able be to control both of the operation to transmit or can also able to
change the polarized light.
As mentioned above that we need to take two polarized glass pieces filter in the making of the liquid
crystal. The glass which does not have a polarized film on the surface of it must be rubbed with a special
polymer which will create microscopic grooves on the surface of the polarized glass filter. The grooves
must be in the same direction of the polarized film. Now we have to add a coating of pneumatic liquid
phase crystal on one of the polarized filter of the polarized glass. The microscopic channel cause the first
layer molecule to align with filter orientation. When the right angle appears at the first layer piece, we
should add a second piece of glass with the polarized film. The first filter will be naturally polarized as
the light strikes it at the starting stage.
Thus the light travels through each layer and guided on the next with the help of molecule. The molecule
tends to change its plane of vibration of the light in order to match their angle. When the light reaches to
the far end of the liquid crystal substance,it vibrates at the same angle as that of the final layer of the
molecule vibrates. The light is allowed to enter into the device only if the second layer of the polarized
glass matches with the final layer of the molecule.
Working:
The principle behind the LCD’s is that when an electrical current is applied to the liquid crystal molecule,
the molecule tends to untwist. This causes the angle of light which is passing through the molecule of the
polarized glass and also cause a change in the angle of the top polarizing filter. As a result a little light is
allowed to pass the polarized glass through a particular area of the LCD. Thus that particular area will
become dark compared to other. The LCD works on the principle of blocking light. While constructing

8. the LCD’s,a reflected mirror is arranged at the back. An electrode plane is made of indium-tin oxide
which is kept on top and a polarized glass with a polarizing film is also added on the bottom of the device.
The complete region of the LCD has to be enclosed by a common electrode and above it should be the
liquid crystal matter.
Next comes to the second piece of glass with an electrode in the form of the rectangle on the bottom and,
on top, another polarizing film. It must be considered that both the pieces are kept at right angles. When
there is no current, the light passes through the front of the LCD it will be reflected by the mirror and
bounced back. As the electrode is connected to a battery the current from it will cause the liquid crystals
between the common-plane electrode and the electrode shaped like a rectangle to untwist. Thus the light
is blocked from passing through. That particular rectangular area appears blank.
Advantagesof an LCD’s:
• LCD’s consumes less amount of power compared to CRT and LED
• LCD’s are consist of some microwatts for display in comparison to some mill watts for
LED’s
• LCDs are of low cost
• Provides excellent contrast
• LCD’s are thinner and lighter when compared to cathode ray tube and LED
Disadvantagesof an LCD’s:
• Require additional light sources
• Range of temperature is limited for operation
• Low reliability
• Speed is very low
• LCD’s need an AC drive
Applications of Liquid Crystal Display:
Liquid crystal technology has major applications in the field of science and engineering as well on
electronic devices.
• Liquid crystal thermometer
• Optical imaging
• The liquid crystal display technique is also applicable in visualization of the radio frequency
waves in the waveguide
• Used in the medical applications

9. LED DISPLAY
Detail view of a LED display with a matrix of red, green and
blue diodes
The 1,500-foot (460 m) long LED display on the Fremont
Street Experience in Downtown Las Vegas, Nevada is
currently the largest in the world.
An LED display is a flat panel display, which uses an array of light-emitting diodes as pixels for a video
display. Their brightness allows them to be used outdoors where they are visible in the sun store signs and
billboards, and in recent years they have also become commonly used in destination signs on public
transport vehicles, as well as variable-message signs on highways. LED displays are capable of providing
general illumination in addition to visual display, as when used for stage lighting or other decorative (as
opposed to informational) purposes.

10. Defination:
Light emitting diode
Blue, green, and red LEDs in 5 mm diffused case
Workingprinciple Electroluminescence
Invented H. J. Round(1907)[1]
OlegLosev (1927)[2]
James R. Biard (1961)[3]
Nick Holonyak (1962)[4]
First production October 1962
Pin configuration Anode andcathode
Electronic symbol
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction diode that
emits light when activated. When a suitable current is applied to the leads, electrons are able to recombine
with electron holes within the device, releasing energy in the form of photons. This effect is called
electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined

11. by the energy band gap of the semiconductor. LEDs are typically small (less than 1 mm2) and integrated
optical components may be used to shape the radiation pattern.
Working:
An LED screen is actually an LCD screen,but instead of having a normal CCFL backlight, it uses light-
emitting diodes (LEDs) as a source of light behind the screen. An LED is more energy efficient and a lot
smaller than a CCFL, enabling a thinner television screen. Marketing made a lot of fuss about LED TVs,
but it is only the backlight that changed, so there is actually no picture quality improvement over a normal
LCD screen.
There are three main configurations of LED as backlights for television screens:full array, edge lit, and
direct lit.
Full array
Full array LED backlight
This method is considered the best LED backlight type, but can only be found on a limited number of
models.
In a full array LED screen,the LEDs are distributed evenly behind the entire screen. This produces a
more uniform backlight and provides a more effective use of local dimming, where it can change the
luminosity of only a specific part of the screen.
In some TVs,like Sony's XBR line, they use colored LEDs instead of white ones. Technically, this can
create an even greater color range gamut by matching the backlight color with the picture. In practice
though, you will not really see the difference.

12. Edge lit
Edge-lit LED backlight
This is the most common method for LED TVs.
With an edge lit LED screen,the LEDs are placed at the peripheral of the screen. Depending on the
television, it can be all around the screen or only on the sides or the bottom. This allows the screen to be
very thin.
However, it can cause some spots on the screen to be brighter than others, like the edges. This problem is
called flashlighting or clouding. It can be seen when watching a dark scene in a dark environment.
Direct lit
Direct lit LED backlight
This is how the lower-end LED TVs are constructed.
Similarly to the full array method, the LEDs are directly behind the screen. However,there are very few
of them and they cannot be controlled separately to match the luminosity of the picture.
These TVs are not very thin because of the space required behind the screen to add the LEDs and to
diffuse the light over a big area.

13. PLASMA DISPLAY
A plasma display panel (PDP) is a type of flat panel display common to large TV displays 30 inches (76
cm) or larger. They are called "plasma" displays because they use small cells containing electrically
charged ionized gases,which are plasmas.
Plasma displays have lost nearly all market share,mostly due to competition from low-cost LCD and
more expensive but high-contrast OLED flat-panel displays; manufacturing for the United States retail
market ended in 2014, and manufacturing for the Chinese market was expected to end in 2016.
Definition:
Lightning and neon lights are commonplace generators of plasma.
A plasma globe, illustrating some of the more complex plasma
phenomena, including filamentation.
A plasma trail from the Space Shuttle Atlantis during re-entry
into Earth's atmosphere, as seen from theInternational Space Station.
Plasma (from Ancient Greek πλάσμα, meaning 'moldable substance') is one of the four fundamental states
of matter, and was first described by chemist Irving Langmuir in the 1920s. Plasma is a state of matter in
which an ionised gaseous substance becomes highly electrically conductive to the point that long-range
electric and magnetic fields dominate the behavior of the matter. This state can be contrasted with the
other states:solid, liquid, and gas. Unlike the other three states,solid, liquid, and gas, plasma does not
exist freely on the Earth's surface under normal conditions. Plasma can only be artificially generated by
heating or subjecting a neutral gas to a strong electromagnetic field to the point an ionised gaseous
substance becomes increasingly electrically conductive, and long-range electromagnetic fields dominate
the behavior of the matter.

14. Plasma is an electrically neutral medium of unbound positive and negative particles (i.e. the overall
charge of a plasma is roughly zero). Although these particles are unbound, they are not ‘free’ in the sense
of not experiencing forces. Moving charged particles generate an electric current within a magnetic field,
and any movement of a charged plasma particle affects and is affected by the fields created by the other
charges.
Construction & Working:
Composition of plasma display panel
The pixel cells in a plasma TV have things in common with both neon lamps and CFLs. Like a neon
lamp, each cell is filled with tiny amounts of neon or xenon gas. Like a CFL, each cell is coated inside
with phosphor chemicals. In a CFL, the phosphor is the chalky white coating on the inside of the glass
tube and it works like a filter. When electricity flows into the tube, gas atoms crash about inside it and
generate invisible ultraviolet light. The white phosphor coating turns this invisible light into visible white
light. In a plasma TV,the cells are a bit like tiny CFLs only coated with phosphors that are red, blue, or
green. Their job is to take the invisible ultraviolet light produced by the neon or xenon gas in the cell and
turn it into red, blue, or green light we can actually see.

15. Step by step
1. Much like the picture in an LCD screen,the picture made by a plasma TV is made from an array
(grid) of red, green and blue pixels (microscopic dots or squares).
2. Each pixel can be switched on or off individually by a grid of horizontally and vertically mounted
electrodes (shown as yellow lines).
3. Suppose we want to activate one of the red pixels (shown hugely magnified in the light gray
pullout circle on the right).
4. The two electrodes leading to the pixel cell put a high voltage across it, causing it to ionize and
emit ultraviolet light (shown here as a turquoise cross, though it would be invisible in the TV
itself).
5. The ultraviolet light shines through the red phosphor coating on the inside of the pixel cell.
6. The phosphor coating converts the invisible ultraviolet into visible red light, making the pixel
light up as a single red square.
Advantagesof Plasma Display:
• The slimmest of all displays
• Very high contrast ratios [1:2,000,000]
• Weighs less and is less bulky than CTR’s.
• Higher viewing angles compared to other displays [178 degrees].
• Can be placed even on walls.
• High clarity and hence better colour reproduction. [68 billion/236 vs 16.7 million/224]
• Very little motion blur due to high refresh rates and response time.

16. • Has a life span of about 100,000 hours.
Disadvantagesof Plasma Display:
• Cost is much higher compared to other displays.
• Energy consumption is more.
• Produces glares due to reflection.
• These displays are not available in smaller sizes than 32 inches.
• Though the display doesn’t weigh much, when the glass screen,which is needed to protect
the display, is included, weighs more.
• Cannot be used in high altitudes. The pressure difference between the gas and the air may
cause a temporary damage or a buzzing noise.
• Area flickering is possible.
•

17. CONCLUSION
Parameter LCD Plasma
Contrast[does not distinguish
"static" from "dynamic"]
5,000 to 10,000:1[values
dubious][2][resource not
accessible]
5,000,000:1[value unique]
Color depth
6 to 10-bit per subpixel
panels; smaller dot pitch, better
detail
6 to 8-bit per subpixel panels; best
color gamut [resource out of date,
not impartial] [resource out of date;
source not credible/reputable]
Response time
1–8 ms typical (according to
manufacturer data), older units
could be as slow as 35 ms
Less than 1 µs; can get up to 0.001
µs
Frame rate
60 fps typically, some can do
120 fps;
internally, display refreshed at
up to 240 Hz
60 fps typically, some can do 120
fps;
internally, display refreshed at e.g.
480 or 600 Hz
Environmental influences
Prone to malfunctions on both
low (below -4 °F-20 °C) or high
(above 45 °C113 °F)
temperatures
High altitude pressure difference
may cause poor function or buzzing
noises
Flicker
Depends; as of 2013, most
LCDs use PWM(strobing) to
dim the backlight
Does not normally occur due to
high refresh rate.
Size
Up to 108"(2.78m) Up to 150"(3.8m)
Energy consumption and heat
generation
Low
Varies with brightness but usually
higher than LCD
Maintenance
Risky and expensive to repair
due to complexity of the
display; units
with mercury lamps are a minor
environmental hazard
Screen itself cannot be repaired if
the gas used to generate images
leaks
Electro-magnetic radiation
emission
Only emits non-ionizing
radiation.
Emits strong radio
frequency electromagnetic
radiation.

18. Other
The LCD grid can mask effects
of spatial and grayscale
quantization, creating the
illusion of higher image
quality.[33]
Screen-door effects are more
noticeable than LCD when up
close, or on larger sizes;[34]