LED TV


LED-backlit LCD television (called LED TV by Samsung Electronics, Panasonic,Toshiba, Philips, LG Electronics, ProScan and Vizio and not to be confused with true LED displays) is an LCD TV that uses LED backlighting[1] rather than fluorescent lights used in traditional LCD televisions.

The LEDs can come in two forms, Dynamic RGB LEDs which are positioned behind the panel, or white Edge-LEDs positioned around the rim of the screen which use a special diffusion panel to spread the light evenly behind the screen.[2]

LED Backlighting Techniques
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RGB Dynamic LEDs

This method of backlighting allows dimming to occur locally creating specific areas of darkness on the screen. This can show truer blacks, whites and PRs at much higher dynamic contrast ratios, at the cost of less detail in small bright objects on a dark background, such as star fields.[3]
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Edge-LEDs

This method of backlighting allows for LED-backlit TVs to become extremely thin. The light is diffused across the screen by a special panel which produces a uniform color range across the screen.

Sharp also has LED backlighting technology that aligns the LEDs on back of the TV like the RGB Dynamic LED backlight, but it lacks the local dimming of other sets.[4]
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Differences between LED-backlit and CCFL-backlit LCD displays

LED-backlit LCD TVs differ from conventional CCFL-backlit LCD TVs in the following:
They can produce an image with greater dynamic contrast compared with CCFL-backlit LCD TVs.[5]
With Edge-LED lighting they can be extremely slim. Current models on the market can be less than one inch thick.[5]
They can offer a wider color gamut, especially when RGB-LED backlighting is used.[5]
Lesser environmental pollution on disposal.[5]
Higher cost due to current market product placement.[5]
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Technology

TV manufacturers can use an LED backlight instead of the standard Cold Cathode Fluorescent Lamps (LCD-CCFL) used in most LCD televisions. It is important to distinguish this method of simply backlighting a conventional LCD panel, from a hypothetical true LED display, or an OLED display. LCD-based televisions described as 'LED TVs' are vastly different from self-illuminating OLED, OEL or AMOLED display technologies. In terms of the use of the term 'LED TV' in the UK, the ASA (Advertising Standards Authority) has made it clear in prior correspondence that it does not object to the use of the term, but does require it to be clarified in any advertising. There are several methods of backlighting an LCD panel using LEDs including the use of either White or RGB (Red, Green and Blue) LED arrays positioned behind the panel; and Edge-LED lighting, which uses white LEDs arranged around the inside frame of the TV along with a special light diffusion panel designed to spread the light evenly behind the LCD panel.

An LED backlight offers several general benefits over regular CCFL backlight TVs, typically higher brightness. Compared to regular CCFL backlighting, there may also be benefits to color gamut. However advancements in CCFL technology mean wide color gamuts and lower power consumption are also possible. The principal barrier to wide use of LED backlighting on LCD televisions is cost.

The variations of LED backlighting do offer different benefits. The first commercial LED backlit LCD TV was the Sony Qualia 005 (introduced in 2004). This featured RGB LED arrays to offer a color gamut around twice that of a conventional CCFL LCD television (the combined light output from red, green and blue LEDs produces a more pure white light than is possible with a single white light LED). RGB LED technology continues to be used on selected Sony BRAVIA LCD models, with the addition of 'local dimming' which enables excellent on-screen contrast through selectively turning off the LEDs behind dark parts of a picture frame.

Edge LED lighting was also first introduced by Sony (September 2008) on the 40 inch BRAVIA KLV-40ZX1M (referred to as the ZX1 in Europe). The principal benefit of Edge-LED lighting for LCD televisions is the ability to build thinner housings (the BRAVIA KLV-40ZX1M is as thin as 9.9mm). Samsung has also introduced a range of Edge-LED lit LCD televisions with extremely thin housings.

LED-backlit LCD TVs are considered a more sustainable choice, with a longer life and better energy efficiency than plasmas and conventional LCD TVs.[6] Unlike CCFL backlights, LEDs also use no mercury in their manufacture. However, other elements such as gallium and arsenic are used in the manufacture of the LED emitters themselves, meaning there is some debate over whether they are a significantly better long term solution to the problem of TV disposal.

Because LEDs are able to be switched on and off more quickly than CCFL displays and can offer a higher light output, it is theoretically possible to offer very high contrast ratios. They can produce deep blacks (LEDs off) and a high brightness (LEDs on), however care should be taken with measurements made from pure black and pure white outputs, as technologies like Edge-LED lighting do not allow these outputs to be reproduced simultaneously on-screen.

In September 2009 Nanoco Group announced that it has signed a joint development agreement with a major Japanese electronics company under which it will design and develop quantum dots for LED Backlights in LCD televisions.[7] Quantum dots are valued for displays, because they emit light in very specific gaussian distributions. This can result in a display that more accurately renders the colors that the human eye can perceive. Quantum dots also require very little power since they are not color filtered.