Plasma TVs are basically an array of light emitting gas cells sandwiched between two glass sheets. The fact that they do not rely on an external light source to power the display, they can give amazing true black effect.

PRINCIPLE OF WORKING

The basic idea of a plasma display is to illuminate tiny colored fluorescent lights to form an image. Each pixel is made up of three fluorescent lights -- a red light, a green light and a blue light. Just like a CRT television, the plasma display varies the intensities of the different lights to produce a full range ofcolors.

The central element in a fluorescent light is a plasma, a gas made up of free-flowing ions (electrically charged atoms) and electrons (negatively charged particles). Under normal conditions, a gas is mainly made up of uncharged particles. That is, the individual gas atoms include equal numbers of protons (positively charged particles in the atom's nucleus) andelectrons. The negatively charged electrons perfectly balance the positively chargedprotons, so the atom has a net charge of zero.

If many free electrons are introduced into the gas by establishing an electrical voltage acrossit, the situation changes very quickly. The free electrons collide with the atoms, knockingloose other electrons. With a missing electron, an atom loses its balance. It has a netpositive charge, making it an ion.

In a plasma with an electrical current running through it, negatively charged particles arerushing toward the positively charged area of the plasma, and positively charged particles are rushing toward the negatively charged area.

Xenon and neon atoms, the atoms used in plasma screens, release light photons when they are excited. Mostly, these atoms release ultraviolet light photons, which are invisible to the human eye. But ultraviolet photons can be used to excite visible light photons

OPERATION

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, on both sides of the cells. The address electrodes sit behind the cells, along the rear glass plate. The transparent display electrodes, which are surrounded by aninsulating dielectric material and covered by a magnesium oxide protective layer, are mounted above the cell, along the front glass plate.

Both sets of electrodes extend across the entire screen. The display electrodes are arranged in horizontal rows along the screen and the address electrodes are arranged in vertical columns. the vertical and horizontal electrodes form a basic grid.

To ionize the gas in a particular cell, the plasma display's computer charges the electrodes that intersect at that cell. It does this thousands of times in a small fraction of a second, charging each cell in turn.

When the intersecting electrodes are charged (with a voltage difference between them), an electric current flows through the gas in the cell. As we saw in the last section, the current creates a rapid flow of charged particles, which stimulates the gas atoms to release ultraviolet photons.

The released ultraviolet photons interact with phosphor material coated on the inside wall of the cell. Phosphors are substances that give off light when they are exposed to other light.

When an ultraviolet photon hits a phosphor atom in the cell, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. When the electron falls back to its normal level, it releases energy in the form of a visible light photon.

The phosphors in a plasma display give off colored light when they are excited. Every pixel is made upof three separate subpixel cells, each with different colored phosphors, i.e. red, green and blue light phosphor. These colors blend together to create the overall color of the pixel.

By varying the pulses of current flowing through the different cells, the control system can increase or decrease the intensity of each subpixel color to create hundreds of different combinations of red, green and blue. In this way, the control system can produce colors across the entire spectrum.

Plasma panels use pulse-width modulation (PWM) to control brightness: by varying the pulses of current flowing through the different cells thousands of times per second, the control system can increase or decrease the intensity of each subpixel color to create billions of different combinations of red, green and blue.

SPECIFICATION

Average Viewing angle 70Average Black Luminance 0.05 cd/m2Average White Luminance 100 cd/m2Power Supply AC 120 V / 60 HzAverage thickness 2.5Channel capability VHF/ UHF: 2 - 69, CATV: 1 - 135Resolution 1920 x 1080Operating Conditions Temperature: 32 F - 104 F (0 C - 40 C)

Humidity: 20 % - 80 % RH (non-condensing)

ADVANTAGES

1) Capable of producing deeper blacks allowing for superior contrast ratio

2) Wider viewing angles than those of LCD; images do not suffer from degradation at less than straight ahead angles like LCDs. LCDs using IPS technology have the widest angles, but they do not equal the range of plasma primarily due to "IPS glow", a generally whitish haze that appears due to the nature of the IPS pixel design.

3) Less visible motion blur, thanks in large part to very high refresh rates and a faster response time, contributing to superior performance when displaying content with significant amounts of rapid motion.

4) Superior uniformity. LCD panel backlights nearly always produce uneven brightness levels, although this is not always noticeable. High-end computer monitors have technologies to try to compensate for the uniformity problem.

5) Unaffected by clouding from the polishing process. Some LCD panel types, like IPS, require a polishing process that can introduce a haze usually referred to as "clouding".

6) Less expensive for the buyer per square inch than LCD, particularly when equivalent performance is considered.

DISADVANTAGES

1) Earlier generation displays were more susceptible to screen burn-in and image retention. Recentmodels have a pixel orbiter that moves the entire picture slower than is noticeable to the humaneye, which reduces the effect of burn-in but does not prevent it.

2) Due to the bistable nature of the colour and intensity generating method, some people will

notice that plasma displays have a shimmering or flickering effect with a number of hues, intensities and dither patterns.

3) Earlier generation displays (circa 2006 and prior) had phosphors that lost luminosity over time, resulting in gradual decline of absolute image brightness. Newer models have advertised life spans exceeding 100 000 hours, far longer than older CRTs

4) Screen-door effects (black lines between rows of pixels) become noticeable on screen sizes larger than 127 cm (50 in); the effect is more visible at shorter viewing distances.

5) Uses more electrical power, on average, than an LCD TV using an LED backlight. Older CCFL backlights for LCD panels used quite a bit more power, and older plasma TVs used quite a bit more power than recent models.

6) Does not work as well at high altitudes above 2 km due to pressure differential between the gases inside the screen and the air pressure at altitude. It may cause a buzzing noise. Manufacturers rate their screens to indicate the altitude parameters.

7) Plasma displays are generally heavier than LCD, and may require more careful handling such asbeing kept upright.

LCD TV

Liquid-crystal-display televisions (LCD TV) are televis ion sets that use LCD display technology 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 In 2007, LCD televisions surpassed sales of

CRT-based televis ions 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 televis ion display type.

LCDs also have a variety of disadvantages. Other technologies address these weaknesses, including

organic light-emitting diodes (OLED), FED and SED, but as of 2014 none of these have entered

widespread production for TV displays.

LCD televisions produce a black and colored image by selectively filtering a white light. The light was

provided by a series of cold cathode fluorescent lamps (CCFLs) at the back of the screen. Today, most

LCD-TV displays use white or colored LEDsas backlighting instead. Millions of individual LCD

shutters, arranged in a grid, open and close to allow a metered amount of the white light through. Each

shutter is paired with a colored filter to remove all but the red, green or blue (RGB) portion of the light

from the original white source. Each shutterfilter pair forms a single sub-pixel. The sub-pixels are so

small that when the display is viewed from even a short distance, the individual colors blend together to

produce a single spot of color, apixel. The shade of color is controlled by changing the relative intensity

of the light passing through the sub-pixels.

Making of LCD

Though the making of LCD is rather simple there are certain facts that should be noted while making it.

The basic structure of an LCD should be controllably changed with respect to the applied electric

current.

The light that is used on the LCD can be polarized.

Liquid crystals should be able to both transmit and change polarized light.

There are transparent substances that can conduct electricity.

To make an LCD, you need to take two polarized glass pieces. The glass which does not have a

polarized film on it must be rubbed with a special polymer which creates microscopic grooves in the

surface. It must also be noted that the grooves are on the same direction as the polarizing film. Then, all

you need to do is to add a coating of nematic liquid crystals to one of the filters. The grooves will cause

the first layer of molecules to align with the filters orientation. At right angle to the first piece, you

must then add a second piece of glass along with the polarizing film. Till the uppermost layer is at a

90-degree angle to the bottom, each successive layer of TN molecules will keep on twisting. The first

filter will naturally be polarized as the light strikes it at the beginning. Thus the light passes through

each layer and is guided on to the next with the help of molecules. When this happens, the molecules

tend to change the plane of vibration of the light to match their own angle. When the light reaches the

far side of the liquid crystal substance, it vibrates at the same ang le as the final layer of molecules. The

light is only allowed an entrance if the second polarized glass filter is same as the final layer. Take a

look at the figure below.

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.

PRINCIPLE:

When electric voltage is applied to a liquid crystal, it ALTERS THE POLARIZATION OF

LIGHT passing through it. Thus if we put two polarization filters between the liquid crystal such that

light will pass only if the crystal fully rotates the light, we can even block the passing light.

LIQUID CRYSTALS: liquid crystal displays use organic liquid crystal The molecules,whose

macroscopic behaviour resembles that of a liquid. But these crystals also show properties only

found in crystals. They are rodlike and somewhat elongated in structure.

How LCDs Work?

The principle behind the LCDs 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 the LCDs, 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.

Operation of LCD

1. The liquid crystals adjust themselves parallel or perpendicular to the electric field

applied to them.

2. The electric field thus applied to an LCD cell twists the molecules.

3. The twist is (can be made LINEARLY) proportional to the applied voltage.

4. The electric field is applied at right angles to the axes of liquid crystals.

5. When the voltage is applied to the plates, the polarization of light passing through the

crystal can vary from 0 to 90 degree.

LCD BLOCK DIAGRAM LCD is divided into following primary sections :

1.Power Supply: TFT LCD uses triple output power supply.The input to the power supply is AC

and output voltages are 5V,12V and 24V. Each of the three voltages are used for powering

different circuits in LCD. 5V is used for powering power management unit,12V is used for

powering backlight driver circuit and 24V is used for signal conditioning circuits (as the require

more power).

2.Backlight Driver Circuit: This circuit used to drive the backlight generator for the

LCD.Traditional LCDs used cold cathode fluorescent lamp(CFL)s for generating

backlights.Modern LCDs use light emitting diode(LED)s for generating backlight.Backlight driving

circuit consists of three power converters.Backlight LEDs are connected in series and parallel in

the RGB LED backlight modules. LED current/voltage characteristic variations cause brightness

difference. Therefore, dimming control is an important design consideration for LED backlight

applications.Three dimming methods used for the current

regulation of parallel connected LED arrays are 1)Transconductance amplifier dimming

2)Burst Mode dimming and 3)Current Mirror dimming.The transconductance amplifier and

current mirror dimming methods are unsuitable to be used in the highpower LED

backlight design of LCD panels due to the significant conduction losses of the dimming

transistors under dimming operations.

3.LED array: LCD display consists of array of pixels. Each pixel consists of 3 cells

corresponding to 1 of the RGB LEDs. These LEDs are used for backlighting the display.

4.Signal Conditioning board: This block is used for signal processing of video signals given to

the input of the display. The output signal of this block is given to the DRAM flash memory.

5.Power Management Circuit: This circuit is used to power various signal processing circuits in

Signal conditioning Board.

ADVANTAGES:

1. Compact in size

2. Low in weight

3. Low power consumption

4. Suitable for Large displays

5. Suitable for Portable applications

6. Reliability

7. LCD TVs with LED backlight are smaller than plasma TVs

8. No problem at higher altitudes

9. Environmentally friendlyno greenhouse gases emitted unlike Plasma TVs

1. Sharpness

Image is perfectly sharp at the native resolution of the panel. LCDs using an analog input require

careful adjustment of pixel tracking/phase (see Interference, below).

2. Geometric Distortion

Zero geometric distortion at the native resolution of the panel. Minor distortion for other resolutions

because the images must be rescaled.

3. Brightness

High peak intensity produces very bright images. Best for brightly lit environments.

4. Screen Shape

Screens are perfectly flat.

5. Physical

Thin, with a small footprint. Consume little electricity and produce little heat.

Disadvantages

1. More expensive to CRT displays

2. Brightness, contrast and colour resolution of LCDs is poor

3. Additional requirement of light source

4. a limited temperature range of operation (between 0 and 60 C)

5. short operating life

6. slow speed

1. Resolution

Each panel has a fixed pixel resolution format determined at the time of manufacture that can not be

changed. All other image resolutions require rescaling, which generally results in significant image

degradation, particularly for fine text and graphics. For most

applications should only be used at the native resolution of the panel. If you need fine text and graphics

at more than one resolution do not get an LCD display.

2. Inte rference

LCDs using an analog input require careful adjustment of pixel tracking/phase in order to reduce or

eliminate digital noise in the image. Automatic pixel tracking/phase controls seldom produce the

optimum setting. Timing drift and jitter may require frequent readjustments during the day. For some

displays and video boards you may not be able to entirely eliminate the digital noise.

3. Viewing Angle

Limited viewing angle. Brightness, contrast, gamma and color mixtures vary with the viewing angle.

Can lead to contrast and color reversal at large angles. Need to be viewed as close to straight ahead as

possible.

4. Black-Level, Contrast and Color Saturation

LCDs have difficulty producing black and very dark grays. As a result they generally have lower

contrast than CRTs and the color saturation for low intensity colors is also reduced.

Not suitable for use in dimly lit and dark environments.

5. White Saturation

The bright-end of the LCD intensity scale is easily overloaded, which leads to saturation and

compression. When this happens the maximum brightness occurs before reaching the peak of the

gray-scale or the brightness increases slowly near the maximum. Requires careful adjustment of the

Contrast control.

6. Color and Gray-Scale Accuracy

The internal Gamma and gray-scale of an LCD is very irregular. Special circuitry attempts to fix it,

often with only limited success. LCDs typically produce fewer than 256 discrete intensity levels. For

some LCDs portions of the gray-scale may be dithered. Images are pleasing but not accurate because of

problems with black- level, gray-scale and Gamma, which affects the accuracy of the gray-scale and

color mixtures. Generally not suitable for professional image color balancing.

7. Bad Pixels and Screen Uniformity

LCDs can have many weak or stuck pixels, which are permanently on or off. Some pixels may be

improperly connected to adjoining pixels, rows or columns. Also, the panel may not be uniformly

illuminated by the backlight resulting in uneven intensity and shading over the screen.

8. Motion Artifacts

Slow response times and scan rate conversion result in severe motion artifacts and image

degradation for moving or rapidly changing images.

9. Aspect Ratio

LCDs have a fixed resolution and aspect ratio. For panels with a resolution of 1280x1024 the aspect

ratio is 5:4=1.25, which is noticeably smaller than the 4:3=1.33 aspect ratio for almost all other

standard display modes. For some applications may require switching to a letterboxed 1280x960,

which has a 4:3 aspect ratio.

10. Cost

Considerably more expensive than comparable CRTs.

USES

1. Pocket TV receivers and TV picture tube

2. Electronic toys

3. Laptops

4. Digital clocks and watches

5. Microwave ovens

6. CD players

7. Video cameras

LED TV

Working

The LED TV is a more advanced version of the LCD TV. While both types of TV rely on LCD

technology and have flat-panel designs, the online review resource, TopTenReviews notes, "LED TVs

are slimmer, brighter, and more detailed than your traditional LCD TV." LED TVs function by

illuminating LCD panels with LED backlighting. However, not all LED TVs utilize the same type of

LED backlighting.

LCD Technology

Liquid crystal display is a form of visual display technology that functions by sandwiching a layer of

liquid crystals between two transparent electrodes -- or conductive surfaces. Liquid crystals are

specialized molecules that flow like liquids but polarize light like solid, crystalline structures. An LED

TV can alter the alignment of these liquid crystals by applying an electric current to small, specific

areas of the liquid crystal layer. By altering the arrangement of the liquid crystals, an LED can control

how the layer transmits the light that flows from the TV's backlighting. In this way, an LED TV can

generate on-screen imagery. While a traditional LCD TV relies on the same technology, an LED TV

utilizes a more advanced form of backlighting. LED Lighting An LED TV illuminates its LCD panel

with light-emitting diodes. LEDs consist of small semiconductors, which glow during exposure to

electric current. Specifically, this current flows between LED anodes, which are positively charged

electrodes, and LED cathodes, which are negatively charged electrodes. In contrast, a traditional LCD

TV utilizes fluorescent lamps for acklighting. These lamps function by using mercury vapory to create

ultraviolet rays, which in turn cause the phosphor coating of the lamps to glow. LEDs have several

advantages over fluorescent lamps, including requiring less energy and being able to produce brighter

on-screen colors.

OPERATION

The LED TV is a more advanced version of the LCD TV. While both types of TV rely on LCD technology and have flat-panel designs, the online review resource, TopTenReviews notes, "LED TVs are slimmer, brighter, and more detailed than your traditional LCD TV." LED TVs function by illuminating LCD panels with LED backlighting. However, not all LED TVs utilize the same type of LED backlighting.

LED LightingAn LED TV illuminates its LCD panel with light-emitting diodes. LEDs consist of small semiconductors, which glow during exposure to electric current. Specifically, this current flows between LED anodes, which are positively charged electrodes, and LED cathodes, which are negatively charged electrodes. In contrast, a traditional LCD TV utilizes fluorescent lamps for backlighting. These lamps function by using mercury vapory to create ultraviolet rays, which in turn cause the phosphor coating of the lamps to glow. LEDs have several advantages over fluorescent lamps, including requiring less energy and being able to produce brighter on-screen colors.

Full-Array vs Edge-LitNot all LED TVs utilize LEDs in the same way. As of 2011, there are two primary forms of LED lighting technology that LED TVs can utilize: full-array LED backlighting and edge-lit LED backlighting. Also known as local-dimming technology, full-array technology employs arrays or banks of LEDs that cover the entire back surfaces of LED TV screens. In contrast, edge-lit technology employs LEDs only around the edges of LED TV screens. Unlike an edge-lit LED TV, an LED TV with full-array technology can selectively dim specific groups of LEDs, allowing for superior contrast ratio and superior overall picture quality.

Energy ConsumptionAs with any TV, an LED TV needs energy in order for its components to function. Specifically, an LEDTV needs electric current for stimulating the liquid crystals in its LCD panel and for activating its LEDbacklighting. In comparison to standard LCD TVs, LED TVs consume less energy, qualifying many ofthem for the EPA's Energy Star energy-efficiency standard. As the online TV resource LED TV notes,an LED TV will typically consume between 20 and 30 percent less energy than an LCD TV with thesame screen size.

Basic Principle of LED Back lighting :

Figure 1(b) shows the hollow type structure in which an LGP is used to reduce the thickness of thelight-mixed zone. The good qualities of this type pertain to its compact shape, high luminance and goodthermal dissipation. Figure 1(c) shows the edge-light structure commonly used in a small-scale LCDpanel. This type is of compact shape and low power consumption, so it is suitable for notebook PCsand personal digital assistant (PDA) products. There are two types of LEDs for backlight sources, thewhite-light LEDs and RGB LEDs. The white-light LED is composed of a blue LED coated with yellowphosphor. Simple driving feature make it as a popular choice for new generation of LCD backlightsources in portable display products. Its color filter divides the emitted white light into RGB sub-pixelsto present color pictures. Thicknesses of RGB sub-pixels must be adjusted according to thecorresponding wavelengths to correct the white balance on LCD panel. This results in the difficulty ofmanufacturing process. The white-color point may vary after a long working time. Thus, the RGBLEDs mixing three-color lights to white light are more suitable for medium-scale, or even large-sizescreens. White balance of the LCD panel with RGB LED backlight can be easily corrected byregulating the emission luminance of the RGB LEDs individually.

APPLICATIONS OF LED

Some applications of our LED Display Systems To electronically display Real Time Clock & Temperature for your daily visitors. LED Display Boards at Railways Stations & Airports. Display Board to display daily gold, interest and foreign exchange rates. To display promotional schemes for FMCG / Corporate. LED Display systems at Shopping malls & retail stores. Display Boards at Clubs & multiplexes. Display Board at Trade Fairs & Exhibitions. Display Board to display information at Hotels, Hospitals, Institutions, Schools and Banks

ATMs etc. Display Board to display traffic information. Pedestrian countdown display system for maximum pedestrian safety. Amusement Parks & Zoo's Display Systems.

Applications of LED TVs :

Outdoor dynamic advertisement Crowded areas, concert halls, holiday resorts Presentations Exhibitions Meetings Train stations, airports Metro stations Sport arenas and halls Congested city streets and squares TV studios Modern dynamic video signs and banners

Major advantages of LED TVs :

Dynamic full color video advertisement of high quality Possibility of live video broadcast High quality and high resolution of screens (up to 1280x960 pixels) Modular construction of screens Extra bright LEDs High brightness and contrast of displayed image High reliability and durability Possibility to increase screen size at a later stage Possibility to link screens into network and control them from unified center

Disadvantages of LED TVs :

LED TVs currently cost as much as twice as much as the standard LCD or plasma sets.

Specification :

LED LightingFull-Array vs Edge-LitEnergy Consumption