We explain how an OLED TV differs from the 'LED' TV that you may already have in your living room
If one product generated more excitement than any other in recent months, it's the announcement of 55” OLED TVs from both LG and Samsung.
This particular display technology has been in development for a number of years but whilst smaller screen sizes had been launched previously, these are the first examples of big screen OLED TVs. The consumer electronics industry has invested a great deal of money in the development of OLED and there are many who feel that this revolutionary technology represents the future for the display industry. With so much hype surrounding OLED, you could be forgiven for being curious about the technology. How exactly does it work and what benefits does it actually offer? What is an OLED TV?
With so much hype surrounding OLED, you could be forgiven for being curious about the technology.
Well, an Organic Light-Emitting Diode (OLED) is a device which is composed of a layer of organic compounds which emit light in response to an electric current. The definition of a diode is a two terminal electronic component and in the case of a Light-Emitting Diode (LED), when a current is passed between the two terminals it glows, much like a light bulb. So with an Organic LED the conducting material is the layer of organic compounds which glow when a current is passed between the two terminals, and since one of these terminals is transparent it creates a screen.
This basic OLED technology has been around for a number of years but it is the recent development of active-matrix OLEDs that has resulted in the creation of high definition panels and larger screens. This active-matrix is a thin-film transistor grid which sits at the back of the panel and can switch each individual pixel on or off, thus allowing an unprecedented level of control over the image. A high definition image has a resolution of 1920 x 1080 and is composed of over two million pixels which, thanks to the active-matrix, can be individually illuminated.
An Organic Light-Emitting Diode (OLED) is a device which is composed of a layer of organic compounds which emit light in response to an electric current.
A traditional Liquid Crystal Display (LCD) TV uses a panel that is comprised of a layer of liquid crystal that is sandwiched between two polarised filters and illuminated by a light source behind the panel. By passing an electrical current through the liquid crystal layer, the individual pixels can be opened and closed to allow the light from the back light through. The problem is, that whether the LCD TV is using a Cold Cathode Fluorescent Lamp (CCFL) or an LED, the light has to pass through the LCD panel. Since the LCD panel can never go completely black, even when the pixels are all shut off, an LCD TV tends to suffer from poor blacks. This in turn affects the difference between black and white, which is referred to as the contrast ratio.
The manufacturers have tried to address this by using ‘local dimming’ on LCD TVs that use LEDs as a backlight, so that the LEDs can turn off in the dark areas of the image. Whilst this does improve the perceived black levels, due to the limited number of zones that can be dimmed, it also introduces additional problems like ‘haloing’, where a light object against a dark background appears to glow.
An OLED TV is capable of incredibly deep black levels and as such can achieve a much higher contrast ratio than an LCD TV or even a plasma.By contrast, an OLED display works without a backlight as the organic compounds in the screen are self-illuminating when an electrical current is applied, which in that sense makes it more like a Plasma TV than an LCD TV. Thanks to the self-illuminating nature of the technology, an OLED TV is capable of incredibly deep black levels and, as such, can achieve a much higher contrast ratio than an LCD TV, or even a plasma. One of LCD’s big advantages is its brightness which can be very useful in rooms with ambient light and whilst an OLED TV will emit less light than an LCD TV, it does perform much better in a dark room or one with very little ambient light.
The lack of a backlight is only one of the advantages of OLED, however, other benefits include incredibly light and thin displays, LG’s new 55” OLED TV is only 4m deep for example, as well as much better energy efficiency. An OLED TV also offers a much wider viewing angle when compared to an LCD TV and a much faster response time, with LG’s new 55” OLED TV being 1,000 times faster than its LCD equivalent. This faster response time, which is the time it takes for a pixel to change, should result in better motion handling and when combined with the excellent blacks, higher contrast ratio and wider colour gamut, can deliver some of the best TV images you will see.
Of course, OLED is a new technology and as such it is still developing and still has a number of issues to be aware of. The most obvious of these is the actual cost of the displays, which reflects how difficult it is to produce the OLEDs themselves. There is also the problem of a limited lifespan, especially where blue OLEDs are concerned. Up until now blue OLEDs have had life spans of around 14,000 hours which is considerably less than the 25,000 to 40,000 hours seen with LCD and Plasma technologies. Now, in fairness, 14,000 hours still equates to about 8 hours of TV watching a day for 5 years but it is seen as an issue.
In addition, the blue OLED tends to degrade faster than the other colours (red and green), which will result in a change in the colour balance of the display. Finally, the brightness of each OLED pixel fades depending on the content being displayed. The varied lifespan of the organic dyes can cause a discrepancy between the intensity of red, green and blue, which could lead to an image persistence called burn-in. To avoid all these problems, LG’s new 55” OLED screen uses a white OLED which won’t degrade unevenly or suffer from burn-in and has a lifespan closer to the other more established TV technologies.
Despite the benefits of OLED, there are still a number of issues relating to cost and lifespan.So there you have it, an OLED TV is a brand new type of display using an exciting new technology and should not be confused with an ‘LED’ TV which is nothing more than a misleading marketing name for an LCD TV that uses an LED backlight. An OLED TV uses self-illuminating organic compounds to deliver far superior images when compared to LCD TVs, with excellent blacks, higher contrast ratios and much faster response times. It also offers incredibly thin displays, as well as wider viewing angles and far better energy efficiency.
Whilst there are still some question marks surrounding the lifespan of the panels and the dangers of burn-in, the biggest issue at the moment is the cost of production. Due to these costs, if you want to buy an OLED TV in 2013, you’re going to need deep pockets but as the production costs fall and availability increases, the prices will inevitably drop and eventually all of us will be able to enjoy this incredible new technology.
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