Screen Technologies 101

– By Yogesh Chellappa (Tech Team)

Ever wondered how that smartphone screen or your television screen works? Find yourself frequently bamboozled by LED, LCD or AMOLED?

Let’s dive into ’em and have a quick run-down.

LCD:

Liquid crystal display, essentially consists of a twisted layer of crystals (you don’t say) sandwiched between a pair of electrodes and couple of transparent filters which align and realign when polarised by an external back-light. The crystals twist in varying degrees when illuminated by the backlight and turn into various hues you discern on your screen.

The most common way of backlighting involves placing series of horizontal tubings behind the screen which provide the illumination.

 

Though pretty easy to mass produce, LCDs have notoriously poor viewing angles and motion blur is perceptible to the eye.

The more obvious disadvantage can be attributed to the fact that they need an external backlighting to display, which immediately puts a frown on smartphones manufacturers who need to be battery conscious.

Despite these, they’re still pretty popular in calculators and low-end televisions

LED:

Now let’s look at the obvious disadvantage of LCDs. Say you want to display this on your screen.

Obviously the first backlighting tube sitting pretty behind the screen would be powered on while the rest don’t.

But what if you had to display this?

The backlighting system has to be intelligent enough to adapt accordingly and you can easily say that the colour fidelity would never be spot on to display cleanly. You would notice what is called ‘colour bleeding’ ie, the blacks would not be a true deep shade of black but rather greyish blacks and neither would the whites appear stark white due to some light ‘bleeding’ or leaking onto those crystals.

So what if you used a smaller backlighting system instead of tubes?

Something like …hmmm… an LED?

That’s your LED TV for you.

Imagine lots and lots of LEDs behind the same crystal screen each of which can be independently lit or not.

                     

Now an image like the chessboard-like pattern would not trouble your backlighting system. Only those necessary LEDs would be powered on while the rest remain mute.

Notice the very image on a Sony LED TV and an LG LED TV side by side. Don’t the blacks look impossibly deep and crisp?

Have you ever wondered how your TV manages to pack all those panels, filters et al and still manage to look so blasted thin?

Sony played a major role in pioneering these kind of TVs in 2004. And how did they do it? 

They placed the LEDs on the edge of the screen where the frame around the television lies. The added bulk of the backlighting system disappears and the the size shrinks. This kind of televisions are called edgelit LED Tvs.

                     

LEDs all around the frame now provide the backlighting and the TV is slim. All are happy. Wait. Are we now?

These kind of images are handled with aplomb by the edgelit system.  

               

The edges are lit and the whites look crisp and starkly lit. The blacks are deep and look sharp.

Now what if you had to display this?

       

                     

The lighting system would struggle, won’t you say?

The world woke up to the rise of the newest kid on the block: the AMOLED.

AMOLED:

Your backlit LED television had a plethora of LEDS to provide backlighting. What if now each LED was shrunk down to the size of a pixel? Oh and let’s chuck out all the crystals too while we are at it.

Lo and behold, that’s an AMOLED panel for you.

Each pixel in an AMOLED is capable of being lit individually and with varying colours depending on the intensity of current passing through them.

This translates to superior battery life as only those necessary pixels need to be lit and the rest can be turned off.

Another added advantage would be superior contrast ratios. Blacks would be perfectly black. The screen would essentially be ‘off’ in those parts.

AMOLEDs too have their fair share of problems. They are difficult to manufacture and the brightness is comparatively lesser due to the absence of a dedicated lighting system.

                     

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