SUBJECT: AUDIO-VIDEO SYSTEMS. TOPIC: LCD,LED AND PLASMA TV. PREPARED BY: ENROLLMENT NO: 1.HIMANI AHIRWAR HENRY JOHN NIDHI KHAKHER ATHULYA ROSE AUGUSTINE

CONTENT 1.INTRODUCTION TO LCD TV 2.WORKING PRINCIPLE OF LCD TV 3.ADVANTAGES AND DISADVANTAGES OF LCD TV 4.INTRODUCTION TO LED TV 5.WORKING PRINCIPLE OF LED TV 6.ADVANTAGES AND DISADVANTAGES OF LED TV 7.INTRODUCTION TO PLASMA TV 8.WORKING PRINCIPLE OF PLASMA TV 9.ADVANTAGES AND DISADVANTAGES OF PLASMA TV 10.COMPARISON BETWEEN LCD,LED AND PLASMA TV 2

Liquid crystals (LCs) are matter in a state that has properties between those of conventional liquid and those of solid crystal. A liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. LIQUID CRYSTALS(LCs) 3

1.LCD Panel is based on A light valve for each pixel that turn the light on, off, or an intermediate level. 2. Grid of such light valve for the LCD display panel. 3. A back light and display enhancement films create the illumination. LCD (LIQUID CRYSTAL DISPLAY) 4

1. Applying voltage to the electrodes changes the level of illumination in each sub-pixel. 2.The panel is sandwiched between a. Front surface films to enhance display property b. Backlight LIQUID CRYSTAL DISPLAY: 5

HOW DOES LCD WORKS?? 6

How pixels are switched off: 1. Light travels from the back of the TV toward the front from a large bright light. 2. A horizontal polarizing filter in front of the light blocks out all light waves except those vibrating horizontally. 3. Only light waves vibrating horizontally can get through. 4. A transistor switches off this pixel by switching on the electricity flowing through its liquid crystal. That makes the crystal straighten out (so it's completely untwisted), and the light travels straight through it unchanged. 7

5. Light waves emerge from the liquid crystal still vibrating horizontally. 6. A vertical polarizing filter in front of the liquid crystal blocks out all light waves except those vibrating vertically. The horizontally vibrating light that travelled through the liquid crystal cannot get through the vertical filter. 7. No light reaches the screen at this point. In other words, this pixel is dark. 8

How pixels are switched on: 1. The bright light at the back of the screen shines as before. 2. The horizontal polarizing filter in front of the light blocks out all light waves except those vibrating horizontally. 3. Only light waves vibrating horizontally can get through. 4. A transistor switches on this pixel by switching off the electricity flowing through its liquid crystal. That makes the crystal twist. The twisted crystal rotates light waves by 90° as they travel through it. 9

5. Light waves that entered the liquid crystal vibrating horizontally emerge from it vibrating vertically. 6. The vertical polarizing filter in front of the liquid crystal blocks out all light waves except those vibrating vertically. The vertically vibrating light that emerged from the liquid crystal can now get through the vertical filter. 7. The pixel is lit up. A red, blue, or green filter gives the pixel its colour. 10

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Advantages of LCD tv: 1. Sharpness Image is perfectly sharp at the native resolution of the panel. By using analog input require careful adjustment of pixel tracking/phase in LCDs 2. Geometric Distortion At the native resolution of the pannel there is zero geometric distortion. Minor distortion for other resolutions because the images must be rescaled. 3. Brightness By using very bright images high peak intensity is produced. Best for brightly lit environments. 12

Aspect Ratio: The aspect ratio and resolution are fixed. Contrast: Lower contrast than CRTs due to a poor black-level. Resolution: Works best at the native resolution. The native resolution can not be changed. All other resolutions require adjusting procedures which can cause considerable deterioration of the image. be carefully adjusted Disadvantages of LCD tv: 13

Viewing Angle: Restricted viewing angles. Viewing angles affect the brightness, contrast and colors shown. Wide angles can lead to contrast and color reversal. Cost: Considerably more expensive purchase price than comparable CRTs. (Cheaper lifetime cost: lasts about 13, ,000 more hours than a typical CRT.) White Saturation: Saturation and compression can occur due to the bright-end of the intensity scale becoming overloaded. 14

An LED display is a flat panel display, which uses an array of light-emitting diodes as pixels for a video display. LED displays are capable of providing general illumination in addition to visual display. LED DISPLAY: 15

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. 16

There are three main configurations of LED as backlights for television screens: full array, edge lit, and direct lit. 1. 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. 17

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. 18

2. 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. 19

However, it can cause some spots on the screen to be brighter than others, like the edges. This problem is called flash lighting or clouding. It can be seen when watching a dark scene in a dark environment. 20

3. 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. 21

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. 22

What are the advantages of LED TVs? The LCD technology is the same in the cathode fluorescent lamp lit TVs and the LED lit TVs, but the LED lighting of the picture results in a sharper picture, more energy efficient using about 40% less electricity than a standard LCD TV, the LED backlighting system has no delay or warm up time, and the LED lit TVs are much thinner than the traditional LCD or plasma TVs. For example one of the Sony LED TV’s is only 9.9mm thick. Advocates of the LED technology say the LED TVs combine the best of plasma and LCD TVs. LED TVs show contrast similar to a plasma TV and are brighter than an LCD TV. 23

What are the disadvantages of LED TVs? The downside is the LED TVs currently cost as much as twice as much as the standard LCD or plasma sets. Most consumers cannot discern any significant difference between the plasma TV and LED TV pictures and plasmas, at least today, are a lot cheaper. Prices on the LED TVs are anticipated to come down as the competition in the LED TV market increases. 24

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 DISPLAY 25

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). How does plasma works? 26

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. 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. 27

1. Excellent brightness: Because plasma displays use the direct lighting of phosphors (instead of a backlighting system in LCDs), they can have an extremely bright and crisp picture. Because each pixel is controlled directly by the electrical grid behind the plasma cells, the brightness tends to be extremely even across the screen. 2. High resolution: Most plasmas these days are at least 720p capable and many are 1080p capable. Just about all plasma displays on the market are 16:9 aspect ratio sets, which is also essential for HDTV viewing. ADVANTAGES OF PLASMA DISPLAY: 28

3. PC monitor-capable: Most plasma displays can be plugged directly into any PC (not just home theatre PCs with special TV video cards) to act as a gigantic PC monitor. 4. Progressive by nature: Plasma systems don’t use a scanning electron beam to create a picture. Instead, all the pixels on the screen are lit up simultaneously. So progressive video sources display progressively on any plasma system. 5. A wide viewing angle: Plasma displays have a good picture even when you are sitting “off axis” (not perpendicular to the screen surface). In a smaller room, where some of the seating might be at an acute angle from the screen, the wide viewing angle can be a big plus. 29

1. Susceptible to burn-in: Any system that uses a phosphor screen to display video can fall victim to phosphor burn-in. If you do a lot of video gaming or stock or news ticker viewing, you need to be aware of this fact. Manufacturers of plasma TVs have made great strides in reducing the possibility of burn-in, and many plasma TVs have burn-in fix-it programs that generate a series of images onscreen designed to remove any minor burn-in from your screen. DISADVANTAGES OF PLASMA DISPLAY: 30

2. Shorter life span: Another phenomenon of any phosphor-based display system is that eventually the phosphors “wear out” or lose their brightness. Given the considerably higher cost of a plasma, your cost per hour of viewing is much higher. 3. Poor reproduction of black: Like LCDs, plasma displays have a hard time reproducing black, so black scenes end up being reproduced as shades of gray. 31

1)Contrast Ratio By contrast ratio we mean the ability to show high contrast areas i.e. the blacks and whites of the picture. TVs with good contrast ratios are able to shows the difference between dark and light areas very well. Here the plasma TV is one hand up than the LCD and LED TVs. The plasma cells automatically turn off on the darker parts. In case of LCD since only one crystal is there, the backlight made of CCFL only dims and hence the dark areas aren’t that appealing. Where as in LED TVs the LED turns them off and hence is better than the LCD. So in contrast ratio plasma is best, and then is LED and LCD at the last. Comparison in Features of an LCD, LED and Plasma TV 32

2)Viewing Angle The angle from which we can be view the image on a TV is called the viewing angle. All viewers cannot always sit in the front and hence viewing angle is also an important aspect while buying a TV. Here again Plasma screen wins the race. Then comes the LED and last is the LCD because there is considerable loss of color in LCD from a side angle. 3)Colour All the TVs have similar no. of colours, but if we consider an LED with coloured backlight it would show better pictures. 33

4)Motion The refresh rate of plasma cells is very fast and hence the plasma TVs hold an upper hand here. But the LCD and LED makers are improving on this aspect as they have introduced the new higher 'hz' count. 5)Power Consumption In power consumption the LED TVs are winners. This is because the LED backlight requires less energy to light up and hence is more efficient. In case of plasma TV, since there are many cell each cell (each sub- pixel) consumes power to get lightened up, and hence requires a lot of power. Whereas, an LCD has a single crystal. Hence, requires less power. 34

6)Lifespan The quality and brightness of Plasma TVs fade out in a very short span of time. Another thing with Plasma TVs is that, it has had a higher rate of screen burn -in. This is not the case with the LED and LCD TVs. The lifespan of LED and LCD is dependent on the backlight, but it is far better than the plasma TVs. Since the lifespan of LED is still untested, as it is a new technology, LCD holds an upper hand here. 7)Price of the sets LED TVs are the most expensive TVs. As compared to plasma and LCD, it is a new technology and the volume of its production is still low. The cost of an LED is almost double the cost of an LCD TV. The Plasma TVs are the cheapest among the three. 35

36 Thank You