There are LCD TVs and there are LED TVs – but more often than not, they're one and the same! Modern LCDs use LED technology, and this guide explains how.
LED - The End of LCD TVs?
LCD TVs have been around for years now and have so far survived the arrival of plasma TVs. That looks all set to change with the arrival of LED TVs.
Or does it?
Well certainly not yet. LED (light emitting diode) TVs are in fact themselves LCD (liquid crystal display) TVs that use LED (light emitting diode) technology to improve the displayed image through a technique known as “back-lighting”. Various models of TV use a couple of different ways to do this, and the introduction of this technology (first seen on the Sony WEGA in 2004) has seen this type of television maintain popularity as an alternative to plasma.
A standard LCD TV or display is lit by means of a row of tubes - Cold-Cathode Fluorescent Lamps (known as CCFL) – positioned in rows horizontally behind the LCD display. This method is fine for smaller devices, but results in poorer visual quality on larger screens, with problems such as noticeable shading around the frame.
Backlighting Methods
There are two different types of LED TV back-lighting: direct and edge.
Edge Back-lighting
This type of LCD TV employs an array of LEDs that are positioned in the frame to produce a beam of strong white light which is cast parallel to the display. Using edge-lighting allows for the production of thinner screens – however there is a trade-off, with picture quality often suffering.
Direct Back-lighting
Critically a more popular choice, direct-lighting employs many LEDs mounted directly behind the display, aiding the picture quality by producing superior image resolution, particularly in darkly lit images. For instance, a starry night can be represented well via a direct-lighting LCD TV as the stars are enhanced by the LEDs, while in portions of the display where there are no stars the LEDs are disabled.
LCDs Use LED Technology
So – the issue isn’t between LCD vs LED displays, rather old-style LCDs, edge-lighting LEDs and direct-lighting LEDs. Generally speaking, the direct method of back-lighting produces the superior image, but there are other advantages such as improved viewing at an angle - important in a large room - and in TVs where RGB (red, green, blue) colored LEDs are used in preference to white LEDs, color reproduction is vastly improved.
Note that any LED LCD TV will be more expensive to run than a standard LCD display.
The future meanwhile might well see the successful adoption of OLED (organic light emitting diode) technology, a new method of image display already used on some smaller monitors, mobile devices and laptops. OLED provides a tonally more realistic image which many believe will be gentler on the viewer's eyes than harsh backlighting...