A big success story of 2009 is the Samsung LED TV series. Sales of LED TVs has exceeded Samsung’s own target of 2 million units for 2009, the actual figure was up by over 25% with Samsung selling over 2.6 million LED TV units. This success can be attributed to the impressive results produced by Samsung LED TVs coupled with a vigorous advertising campaign. On the back of this success the popularity of this new technology is set to rise even further with Samsung looking to improve and expand their range of LED TVs and cement their place as the market leader in the LED TV market.
However, maybe this new form of television technology is not all it seems. This is because the term LED TV is not the most accurate term to describe this new form of television. Without looking into what technologies are behind this new range of televisions, the phrase LED TV on its own may indicate that this type of television is a ‘true’ LED TV or display. This is a kind of display where LEDs are the primary component that produces the images displayed, ie rather than using an LCD panel in the television, a matrix of LEDs is used to produce the images that are displayed. However as it stands ‘true’ LED TVs aren’t really possible at the moment because of the size of LEDs. The use of LEDs in this way is limited to very large screens for advertising and public events etc.
If you were to look a little deeper and read the LED TV related advertising materials you will see that the use of light emitting diodes in LED TVs is to provide the light source for the LCD panel. This is because an LED TV is still actually an LCD TV, all be it one which uses LEDs for the back or edge lighting. Knowing this fact may leave you feeling a little deceived, a more accurate term to describe an LED TV would be LED-lit LCD TV. The advertisers may argue this term is a long winded and LED TV is a friendlier name. Anyway, whatever the name there are good reasons for the switch to using LEDs in LCD TVs so let us expand on this further.
First you should know that on its own an LCD panel does not produce light. The LCD panel is a matrix of liquid crystal through which light must be passed from another source to make it visible. When an electrical current is applied to the LCD panel the light can be deflected and altered to make the colors and images visible to the viewer.
Up to this point the job of producing the light which makes the LCD panel images visible has been done by cold cathode fluorescent lamps (CCFLs). It is these fluorescent lamps which are being replaced by LEDs. Is there a good reason for this or is it another gimmick that allows TV manufacturers to cynically rebrand old technology as new, giving it a new lease of life and so boosting sales figures? To answer this we must address what are the disadvantages of using fluorescent lamps and does using LEDs improve the situation.
So what are the problems with the use of CCFLs in LCD TVs? There are two main issues, first the inability of LCD TVs to produce truly dark black images and less than perfect color saturation (a limited range of colors). Producing perfect dark blacks is difficult if not impossible when using fluorescent lamps in LCD TVs. This because firstly the lamps must always be switched on, to produce areas of black on screen the light must be blocked by the LCD display so that it is not visible to the viewer. However this process is not perfect and some of the light leaks through making the blacks produced less than perfect. The result is the images on screen may seem slightly blurred or less sharp. In relation to color, the quality of the light produced by fluorescent lamps limits the range of color that it is possible (although since the early days of LCD TV this situation has been improved by producing more effective fluorescent lamps).
To see how LEDs have improved both these deficiencies you need to know a little bit more about their characteristics and how they are used in TVs. Firstly LEDs are smaller electrical components when compared to the size fluorescent lamps or tubes. This means that they can be placed to the rear of LCD panels to create an LED rear-lit LCD TV. Many LEDs are used in a matrix to provide the light required to light the LCD panel and in conjunction with this, LEDs can be individually switched on or off. This solves the problem of light leaking through the LCD display when black images are required, because rather than blocking the light through the LCD display the corresponding LEDs are switched off, this technique is known as ‘local dimming’.
This solution though is not quite so simple because it is too complicated and expensive to produce LED back-lit LCD TVs with enough LEDs that can be controlled individually. Practically TVs with up to approximately 1000 back LEDs can be produced and the LEDs are controlled in blocks rather than individually so that ‘areas’ of improved blackness can be produced. The result is that when images of light and dark are simultaneously displayed a compromise is made because some LEDs are switched on for light areas and others are switched off for dark areas and therefore some light will leak into the blacks from adjacent areas of light. The most noticeable improvement is when the images on screen are largely black.
Another characteristic that the use of LEDs has brought to LCD TVs is the improvement in range of colors, this is known as color gamut. The inherent properties of LEDs mean that the light produced by them is ‘whiter’ that that of fluorescent lamps (to be specific the light produced has a broader spectrum). The practical result is that LED-lit LCD TVs are capable of producing a wider range of colors that consequently enhance the images displayed so that the pictures look more natural and intense to the viewer.
Up to this point we have discussed the use of LEDs in rear lit configurations, however LEDs are also being used in edge-lit LCD TVs also. This in itself has advantages but also reduces the benefits which come from using LEDs in the rear-lit method. The major advantage of using LEDs in edge-lit configurations is that because they are much smaller than fluorescent lamps the physical thickness of the television can be greatly reduced. Manufacturers such as Sony and Samsung have produced televisions that are only 1cm to 2.5cm in thickness. However the benefits that comes from using LEDs in rear-lit LCD TVs (ie local dimming for improved blacks) is no longer applicable. Because the technology of edge-lit LED TVs is less complex they are however cheaper than rear-lit TVs.
Another aspect of side and edge lit LED TVs relates to the type of LEDs that are used for each method. Rear-lit LED TVs use RGB LEDs (red, green, blue LEDs) and edge-lit LED TVs use white LEDs. The significance of this is that the RGB LEDs used in rear-lit TVs produce the whiter light that improves color gamut and the white LEDs used in edge-lit TVs produce a color gamut which is comparable to that of fluorescent lamps used in conventional LCD TVs.
So what is the upshot of all this. Basically rear-lit LED TVs produce the best quality pictures due to the improved color gamut and contrast ratios that results from using RGB LEDs and localised dimming. Edge-lit LED TVs major advantage is that they are ultra thin and have slightly improved picture qualities. Another advantage to using LEDs not already mentioned it that LEDs are more energy efficient and so power consumption is improved by up to 40%, ultimately making them friendlier to the environment. LEDs are also said to be more reliable than fluorescent lamps and their performance does not degrade. Over time fluorescent lamps performance decreases as they become dimmer and they can eventually fail totally. When this happens it is likely that it is not practical or cost effective to replace a failed fluorescent lamp making the television unusable.
With the success that LED TVs have seen in 2009, the television industry seems to be heading in the direction where LED TV will become the mainstream television, replacing conventional CCFL-lit LCD TVs. With this the competition will increase, driving the price down so that LED TV will no longer be in the premium bracket of television making it the more affordable for the average consumer.
As an illustration of this current market leader has big plans for the expansion of Samsung LED TV. In 2010 Samsung aims to multiply the 2009 sales of LED TVs by four times selling 10 million units. They plan on doing this by expanding on the current Samsung LED TV Series 6, 7 and 8 by making a larger range of screen sizes available. Currently Samsung produces TVs with screen sizes available from 32 inches to 55 inches, Samsung plan to expand this range from 19 inches to 65 inches and so catering for a wider audience.
One thing is for sure, 2010 looks to be as busy as ever in the world of high definition television. Competition for a share of the LED TV market is set to be fierce and that’s without even mentioning the emergence of other technologies such as 3D TV and OLED TV.
