Current LCD technology
For many people the rise in popularity of LCD (Liquid Crystal Display) technology was extremely welcome both and home and in the office. Compared to the CRT (Cathode Ray Tube) that previously dominated our desk space LCDs are relatively light weight, have a slender profile don’t have a refresh-rate dependent flicker and have a flatter screen with less geometric image distortion. Key advancements have been made in the key areas such as contrast, colour reproduction and responsiveness. But LCD technologies do seem to lag some way behind some of the higher end CRTs on these key performance credentials and there are always compromises to be made.
The strongest LCD panel type for contrast (Vertical Alignment or VA) is particularly weak when it comes to responsiveness. The kings of colour in the LCD world are the In Plane Switching (IPS) and Plane to Line Switching (PLS) models but these are relatively weak when it comes to contrast and are not the strongest panel type for responsiveness, either. If you are after the fastest response times then really there is no substitute for Twisted Nematic (TN panels) – but these offer relatively weak colour accuracy and restricted viewing angles. Some of the most responsive LCD monitors, such as the Samsung model featured below, offer 120Hz refresh rates to improve motion fluidity further. Some of the best CRT monitors offer some of the contrast advantages of VA, similar or superior colour reproduction to IPS/PLS and better responsiveness than 120Hz TN panel monitors.
A 120Hz LCD monitor
Introducing OLED
The ideal technology would combine the best aspects of all LCD panel types and then build on them without suffering from any of the drawbacks of CRT. Organic Light Emitting Diode (OLED) technology is currently the most credible contender as a future technology to replace ageing LCDs. A significant advantage of OLED is that the pixels are individually and directly illuminated – they are composed of organic materials that ‘glow’ as a current is passed through them. This offers a contrast advantage over all existing technologies, particularly LCD, by allowing the brightness of each individual pixel to be controlled independently. To display black the pixel can shut off entirely whilst it can operate at very high brightness to display bright whites and vivid colours. Because the colours are ‘pure’ and ‘unadulterated’ and come from the red, green and blue subpixels rather than a filtered white light the potential range (gamut), intensity and accuracy of the image is excellent.
Superior quality
Clear advantages
Another key advantage of the OLED matrix is that it is exceptionally thin and can even be made to be flexible should be desire. The end product can therefore be made exceptionally thin without any deterioration in image quality – and because of the direct emission of light close to the surface of the screen the viewing angles are also exceptional. The final big advantage is the exceptional responsiveness of OLED pixels which are quoted as offering 0.01ms response times which compares favourably to 2ms for some of the fastest LCD monitors during certain favourable pixel transitions.
So with all of these advantages why are we still seeing LCD monitors dominate the marketplace? The simple answer is that OLED isn’t quite there yet and there are certain hurdles which manufacturers will have to overcome before it is ready for primetime. The technology is currently expensive and there are concerns regarding degradation of the organic materials – particularly the blue component which tends to degrade more rapidly than the red and green components. As manufacturing processes improve with more efficient methods of production (such as inkjet printing deposition methods) and perhaps new materials these problems should greatly diminish beyond the point of being of concern.
A 55″ OLED screen from Samsung
The future
The two major panel manufacturers, LG and Samsung, are also the two big OLED players and are currently churning out portable devices. They also have much larger screens (as above) in production which will see themselves in the living rooms of the ‘well-healed’ as TV sets. It isn’t yet clear how Samsung’s models will perform long-term and how suitable they would be when connected to a computer but it is certainly positive progress. LG are currently favouring an RGBW (Red, Green, Blue and White) pixel layout which involves shining organic white light through a colour filter (RGB) and directly without a filter (W). Because this does away with coloured organic components you remove the element of differing material degradation rates whilst retaining all of the contrast and responsiveness benefits of conventional RGB designs. The colour reproduction may not be quite on par with Samsung’s implementation but the organic white light should prove favourable to the current phosphor coated LEDs used in modern LCD monitors. In all this would be a great solution until all of the problems with conventional OLEDs are ironed out; really it’s only a matter of time before OLED screens are in a position to start replacing current LCDs.
