HISTORY OF SCREEN
TECHNOLOGY
MONOCHROME CRT
COLOR CRT
SPLİT-FLAP DİSPLAY
FLIP-DISC DISPLAY
MONOCHROME PLASMA DISPLAY
VACUUM FLUORESCENT DISPLAY
DIRECT-VIEW BISTABLE STORAGE TUBE
BRAILLE DISPLAY
FIRST LED DISPLAY
TWISTED NEMATIC FIELD EFFECT LCD
SUPER-TWISTED NEMATIC LCD
THIN FILM TRANSISTOR LCD
FULL-COLOR PLASMA DISPLAY
ORGANIC LED
ORGANIC PAPER
LED(Light Emitting Diode)
A light emitting diode is a semiconductor light
source. Working principle of a LED is
electroluminescence that is when the LED
switched on, electrons are able to recombine with
holes within the device, releasing energy in the
form of photons.
Commercial Development
The first commercial LEDs were commonly used as
replacements for incandescent and neon indicator
lamps, and in seven-segment displays, first in
expensive equipment such as laboratory and
electronics test equipment, then later in such
appliances as TVs, radios, telephones, calculators,
and even watches. Until 1968, visible and infrared
LEDs were extremely costly, in the order of US$ 200
per unit, and so had little practical use.
Commercial Development
The Monsanto Company was the first organization to
mass-produce visible LEDs, using gallium arsenide
phosphide (GaAsP) in 1968 to produce red LEDs
suitable for indicators. Later, other colors became
widely available and appeared in appliances and
equipment. In the 1970s commercially successful LED
devices at less than five cents each were produced
by Fairchild Optoelectronics.
Commercial Development
As LED materials technology grew more advanced,
light output rose, while maintaining efficiency and
reliability at acceptable levels.
Lifetime and Failure
The most common symptom of LED failure is the
gradual lowering of light output and loss of
efficiency. Sudden failures, although rare, can occur
as well.
LED performance is temperature dependent. Most
manufacturers' published ratings of LEDs are for
an operating temperature of 25 °C. LEDs used
outdoors, such as traffic signals, and that are utilized
in climates where the temperature within the light
fixture gets very hot, could result in low signal
intensities or even failure.
Lifetime and Failure
LED light output rises at lower temperatures, leveling
off, depending on type, at around −30 °C. Thus, LED
technology may be a good replacement in uses such
as supermarket freezer lighting and will last longer
than other technologies. However, because they
emit little heat, ice and snow may build up on the
LED light fixture in colder climates. This lack of waste
heat generation has been observed to sometimes
cause significant problems with airport runway
lighting in snow-prone areas.
Applications
Indicators and Signs
Because of their long life, fast switching times and
their ability to be seen in broad daylight, LEDs have
been used in ;
-Brake lights and rear light clusters for vehicles
-Traffic lights
Applications
Indicators and Signs
Red or yellow LEDs are used in
indicator and alphanumeric
displays in environments where
night vision must be retained:
aircraft cockpits, submarine
ship bridges and
astronomy observatories.
Applications
Lightining
LEDs are used increasingly in
aquarium lights. Especially
for reef aquariums, LED lights
provide an efficient light source
with less heat output to help
maintain optimal aquarium
temperatures.
Applications
Lighting
LEDs are the ideal solution for street lighting due to
their long life, directional light, uniform brightness
and illumination.
Applications
Others
Mining operations
Blacklighting for LCD TVs
Lightweight laptop displays
LCD SYSTEMS
A liquid-crystal display (LCD) is a flat panel
display, electronic visual display, or video display
that uses the light modulating properties of
liquid crystals. Liquid crystals do not emit light
directly.
Liquid crystals were first discovered in 1888. By
2008, annual sales of televisions with LCD
screens exceeded sales of CRT units worldwide;
the CRT became obsolescent for most purposes.
They are used in a wide range of applications including
●Computer monitors
●Televisions
●Instrument panels
●Aircraft cockpit displays
●Signage
They are common in consumer devices such as video
players, gaming devices, clocks, watches, calculators, and
telephones, and have replaced cathode ray tube (CRT)
displays in most applications.
Also they are available in a wider range of screen sizes
than CRT and plasma displays.
The LCD screen is more energy efficient and can
be disposed of more safely than a CRT. Its low
electrical power consumption enables it to be
used in battery-powered electronic equipment.
Each pixel of an LCD typically consists of a layer
of molecules aligned between two transparent
electrodes, and two polarizing filters, the axes of
transmission of which are perpendicular to each
other. Without the liquid crystal between the
polarizing filters, light passing through the first
filter would be blocked by the second polarizer.
Since LCD panels produce no light of their own,
they require external light to produce a visible
image. In a "transmissive" type of LCD, this light
is provided at the back of the glass "stack" and is
called the backlight.
Specifications
There are several factors when evaluating an
LCD
Resolution versus range
●Spatial performance
●Temporal/timing performance
●Color performance
●Color depth or color support
●Brightness and contrast ratio
●
Plasma Display
These televisions are light-weight and save a lot of space
• made of 2 sheets of glass with 2 gases stored
between the sheets
• xenon and neon gases
• red, blue and green phosphors (substances
that give off light when struck by light)
plasma display panel (PDP)
• small cells
• containing electrically charged ionized gases,
or what are in essence chambers more
commonly known as fluorescent lamps
*displays are bright (1,000 lux or
higher for the module), have a wide
color gamut
*can be produced in fairly large
sizes—up to 3.8 metres (150 in)
diagonally
*very low-luminance "dark-room"
black level
* life time is 100,000 hours of actual
display time, or 27 years at 10 hours
per day.
native plasma resolutions
*The most common native resolutions for
plasma display panels are 853×480 (EDTV),
1,366×768 or 1,920×1,080 (HDTV).
*upscaling and downscaling algorithms used by
each display manufacturer.
enhanced-definition plasma
television
*Early plasma televisions were enhanceddefinition (ED) with a native resolution of
840×480 (discontinued) or 853×480, and
down-scaled their incoming High-definition
video signals to match their native display
resolution.
ED Resolutions
*Following ED resolutions were common prior
to the introduction of HD displays, but have
long been phased out in favor of HD displays.
High-definition plasma television
• Early high-definition (HD) plasma displays had
a resolution of 1024x1024 and were alternate
lighting of surfaces (ALiS) panels made
by Fujitsu/Hitachi. These were interlaced
displays, with non-square pixels.
•
•
•
•
•
•
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HD Resolutions
1024×1024 (discontinued)
1024×768
1280×768
1366×768
1280×1080
1920×1080
How plasma display works
*millions of tiny cells in between two panels of
glass
*noble gases and a minuscule amount of
mercury gas or plasma
Comparison of Television Display
Technologies
LCD
Disadvantages
• Poor black level: Some light passes through
even when liquid crystals completely untwist,
Advantages
so the best black color that can be achieved
is varying shades of dark gray, resulting in
• Slim profile
worse contrast ratios and detail in the image.
• Lighter and less bulky than rearThis can be mitigated by the use of a matrix
projection televisions
of LEDs as the illuminator to provide nearly
• Is less susceptible to burn-in: Burntrue black performance.
in refers to the television displaying
a permanent ghost-like image due • Narrower viewing angles than competing
technologies. It is nearly impossible to use an
to constant, prolonged display of
LCD without some image warping occurring.
the image. Light-emitting
• LCDs rely heavily on thin-film transistors,
phosphors lose their luminosity
which can be damaged, resulting in
over time and, when frequently
used, the low-luminosity areas
a defective pixel.
become permanently visible.
• Typically have slower response times than
Plasmas, which can cause ghosting and
• LCDs reflect very little light,
blurring during the display of fast-moving
allowing them to maintain contrast
levels in well-lit rooms and not be
images. This is also improving by increasing
affected by glare.
the refresh rate of LCD displays
• Slightly lower power usage than
equivalent sized Plasma displays.
• Can be wall-mounted.
Plasma display
Advantages
• Slim profile
• Can be wall mounted
• Lighter and less bulky than rearprojection televisions
• Achieves better and moreaccurate color reproduction than
LCDs (68 billion (236) versus 16.7
million (224)) colors[
• Produces deep, true blacks
allowing for superior contrast
ratios (up to 1:1,000,000)
• Far wider viewing angles than
those of LCD (up to 178°), images
do not suffer from degradation at
high angles unlike LCD‘s
• Absence of motion blur, because
of very high refresh rates and
faster response times (as fast as
one microsecond) make plasmas
ideal for fast motion video (films
or sports viewing)
Disadvantages
• Susceptible to Screen burn-in and
image retention (however, newer
models have built-in technologies to
prevent this such as pixel shifting)
• Phosphors lose luminosity over time,
resulting in gradual decline of absolute
image brightness (newer models are
less susceptible to this, having lifespans
exceeding 60,000 hours, far longer than
older CRT technology)
• Generally do not come in sizes smaller
than 42 inches
• Susceptible to reflection glare in bright
rooms
• High power consumption
• Heavier than LCDs due to the
requirement of a glass screen to hold
the gases
• Damage to the glass screen can be
permanent and far more difficult to
repair than an LCD